** UnhandledExceptionEventHandler :: OFFICIAL LC / CHATTER THREAD ** - Page 1408 - Computer Technical Help

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09-12-2018 , 08:08 PM

#35176

suzzer99

Save the Cheerleader, Save the World

Join Date: Nov 2005 Posts: 99,984

Code:

/** Console.log out 0-4 inside the timeout */
for (i=0;i<5;i++) {
  let j = i;
  window.setTimeout(function() {
    console.log(j)
  }, j * 100)
}

Btw this seems to work. But not if you do var j instead of let j. Good illustration of var vs. let.

Actually this is all you need to do:

Code:

/** Console.log out 0-4 inside the timeout */
for (let i=0;i<5;i++) {
  window.setTimeout(function() {
    console.log(i)
  }, i * 100)
}

i is being set as a global variable when you don't put let in front of it.

Quote

09-12-2018 , 08:09 PM

#35177

Craggoo

banned

Join Date: Sep 2006 Posts: 12,644

Quote:

Originally Posted by suzzer99

I'm talking about with objects - different but similar problem.

What are the requirements of #1? Does it have to be a for loop? Where can I change the code provided?

There is no real issue with the traverse problem so forget I sort of said there was.

This is what you must output in the setTimeout problem. The console.log *must* be inside the timeout. That is the only thing that makes the problem tricky.

Quote

09-12-2018 , 08:11 PM

#35178

suzzer99

Save the Cheerleader, Save the World

Join Date: Nov 2005 Posts: 99,984

See my answers above.

Quote

09-12-2018 , 08:13 PM

#35179

Craggoo

banned

Join Date: Sep 2006 Posts: 12,644

He never brought up any ES6 topics. With that in mind, I doubt he would allowed me to use let. I'm now kinda intrigued why it works with let but not with var.

Lets say you aren't allowed to use let, do you know how you would accomplish it?

Quote

09-12-2018 , 08:15 PM

#35180

suzzer99

Save the Cheerleader, Save the World

Join Date: Nov 2005 Posts: 99,984

This illustrates the issue I was talking about. You get the final state of the object every time, even though the timeout is set to 0.

Code:

/** Console.log out 0-4 inside the timeout */
const myObj = {};
for(let i=0;i<5;i++) {
  myObj.index = i;
  window.setTimeout(function() {
    console.log(myObj)
  }, 0)
}

I was wrong about console.log itself being async, it's when there's anything async happening in the flow.

Quote

09-12-2018 , 08:18 PM

#35181

suzzer99

Save the Cheerleader, Save the World

Join Date: Nov 2005 Posts: 99,984

Quote:

Originally Posted by Craggoo

Let forces i to be block-scoped, to the for loop.

I'll play around with the var option.

Quote

09-12-2018 , 08:20 PM

#35182

Craggoo

banned

Join Date: Sep 2006 Posts: 12,644

Quote:

Originally Posted by suzzer99

Let forces i to be block-scoped, to the for loop.

I'll play around with the var option.

Its really simple questions like these that illustrate sometimes just how little (or much) you know. You cannot adjust the staggered timeout either. So setting the value to zero is a no-no.

Quote

09-12-2018 , 08:24 PM

#35183

suzzer99

Save the Cheerleader, Save the World

Join Date: Nov 2005 Posts: 99,984

W/o let you have to wrap the setTimeout in a function like this. It works because var is function-scoped but not block-scoped.

Code:

/** Console.log out 0-4 inside the timeout */
for(i=0;i<5;i++) {
  (function () {
    var j = i;
    window.setTimeout(function() {
      console.log(j)
    }, i * 100)
  }());
}

Or just pass i as a function param like this.

Code:

for(i=0;i<5;i++) {
  (function (index) {
    window.setTimeout(function() {
      console.log(index)
    }, index * 100)
  }(i));
}

Note the function doesn't have to be self-executing. It just seemed cleaner that way.

Yeah I probably get hung up on these in interview settings when my brain freezes up. I might get through them but my speed wouldn't wow anyone.

Quote

09-12-2018 , 08:26 PM

#35184

goofyballer

Carpal \'Tunnel

Join Date: Jun 2005 Posts: 70,719

Quote:

Originally Posted by suzzer99

Good illustration of var vs. let.

Heh, I almost put let instead of var in my answer but I think I was swayed by the rest of the code around it being old-school style. Drats!

Quote:

Originally Posted by Craggoo

Quote:

Originally Posted by Craggoo

Lets say you aren't allowed to use let, do you know how you would accomplish it?

Function binding? I forget the exact syntax, but something like

Code:

for (i=0;i<5;i++) {
  window.setTimeout((function(j) {
    console.log(j)
  }).bind(null, i), i * 100)
}

(null first because iirc the first arg to bind sets the value of `this`)
(that may well have the same problem though and idk what the hot codepen sites are to actually try it)

Quote

09-12-2018 , 08:32 PM

#35185

suzzer99

Save the Cheerleader, Save the World

Join Date: Nov 2005 Posts: 99,984

Heh, apparently this works too.

Code:

/** Console.log out 0-4 inside the timeout */
for(i=0;i<5;i++) {
  window.setTimeout(function(index) {
    console.log(index)
  }, i * 100, i)
}

https://stackoverflow.com/questions/...meout-callback

Quote:

In modern browsers, the "setTimeout" receives a third parameter that is sent as parameter to the internal function at the end of the timer.

Example:

var hello = "Hello World";
setTimeout(alert, 1000, hello);

Crazy - I never knew that. Works in node too.

Quote

09-12-2018 , 08:34 PM

#35186

Craggoo

banned

Join Date: Sep 2006 Posts: 12,644

Quote:

Originally Posted by goofyballer

Function binding? I forget the exact syntax, but something like

Code:

for (i=0;i<5;i++) {
  window.setTimeout((function(j) {
    console.log(j)
  }).bind(null, i), i * 100)
}

(null first because iirc the first arg to bind sets the value of `this`)
(that may well have the same problem though and idk what the hot codepen sites are to actually try it)

You have it almost right. I think you had an extra opening parentheses and bind was in the wrong place. The first argument is the `this` value which, in this scenario, we could care less about. We can pass any amount of arguments through when we use bind. By passing it the current value of i, we capture the value as it was (not as it will be).

Code:

for (i=0;i<5;i++) {
  window.setTimeout(function(j) {
    console.log(j)
  }.bind(null, i), i * 100)
}

Edit: yours works too but is generally not how I would use .bind. I would always stick it at the immediate end of a function definition. There's no need to wrap the function in () for .bind to work.

Last edited by Craggoo; 09-12-2018 at 08:42 PM. Reason: whoops

Quote

09-12-2018 , 08:37 PM

#35187

goofyballer

Carpal \'Tunnel

Join Date: Jun 2005 Posts: 70,719

Quote

09-12-2018 , 08:38 PM

#35188

suzzer99

Save the Cheerleader, Save the World

Join Date: Nov 2005 Posts: 99,984

.bind is easily the highest cognitive debt way to solve this, so interviewers will probably love it.

Quote

09-12-2018 , 08:45 PM

#35189

goofyballer

Carpal \'Tunnel

Join Date: Jun 2005 Posts: 70,719

I think C#, oddly enough, works the same way - I've encountered that problem before. I suppose that's one of the reasons C++ is nice with its explicit capture. The same code wouldn't have that problem:

Code:

for (int i = 0; i < 5; i++) {
  lambda = [&] {
    std::cout << i << std::endl;
  };
  // ...do something with lambda
}

The "&" specifies that all variables used inside the lambda (in this case, i) should be captured by reference. Alternatively you could replace that with "=" to make them captured by value.

I suspected, but only now confirmed, that Go works like JS/C#: https://play.golang.org/p/cCKgPpZuMY7

Quote

09-12-2018 , 08:56 PM

#35190

Craggoo

banned

Join Date: Sep 2006 Posts: 12,644

Quote:

Originally Posted by suzzer99

.bind is easily the highest cognitive debt way to solve this, so interviewers will probably love it.

Googling that term brought up a bunch of medical articles instead of an actual definition. I suspect I know what cognitive debt means but you could restate it in more obvious terms?

I can tell you that if you plan on working in React then you better be familiar with call/bind/apply because you'll likely be using them a lot.

I haven't worked in React but I do use .bind quite a lot.

Quote

09-12-2018 , 08:59 PM

#35191

goofyballer

Carpal \'Tunnel

Join Date: Jun 2005 Posts: 70,719

idk, I like bind a lot more from a "look at this code and understand what it's doing" (which I think you're talking about, suzzer?) perspective than the "yo dawg, I heard you like functions so I put a function in your function" solutions.

Quote

09-12-2018 , 09:11 PM

#35192

suzzer99

Save the Cheerleader, Save the World

Join Date: Nov 2005 Posts: 99,984

Right but this is probably the simplest.

Code:

/** Console.log out 0-4 inside the timeout */
for(i=0;i<5;i++) {
  window.setTimeout(function(index) {
    console.log(index)
  }, i * 100, i)
}

Doesn't work in IE8 though. Does work in IE10 and up. Not sure about IE9.

Quote

09-12-2018 , 09:17 PM

#35193

maxtower

Carpal \'Tunnel

Join Date: Sep 2005 Posts: 7,996

Quote:

Originally Posted by goofyballer

I don't know if my company is particularly inaccurate, but my current salary at my current employer is well over what h1bdata/glassdoor show for engineering salaries.

For Netflix, as an example (they seem like a good barometer since they forgo stock for more base salary), Glassdoor says "senior software engineer" averages out to $206k. I'm not leaving my job and moving to the South Bay for that, but I also feel like that's probably significantly undercutting what a senior software engineer actually makes there (remember the $325k figure earlier ITT? I'd probably pack up for that much!).

Maybe part of the problem is that much like how college degrees became ubiquitous, now errybody is a "senior software engineer" and the term is meaningless.

Yeah, these aren't going to be very accurate, but you will hopefully be able to use it to filter some posers. Like if you want to make $200k, you know you don't have to bother with regular programming jobs at companies with a range from 80-120 or whatever. It's just unlikely that they are going to meet your expectations. (Oh they'll still want to know all about your whiteboard skills though)
The smaller a company is, the fewer data points they have, so that will introduce more inaccuracies. These are self reported, and smaller places will be paying their best people to not leave, so those salaries won't be in the mix. Also aren't salaries appreciating at like 10%/yr in the bay area ? If so any salary reported 2 years ago is 20% low.
To get the big salaries a company's product has to either be very valuable (like B2B industrial software) or has to have real scale like millions of users. They have to think they are competing with the FANGs for talent and be funded enough to do so.
Everybody else is trying to skirt by picking up scraps.

Quote

09-12-2018 , 09:33 PM

#35194

Craggoo

banned

Join Date: Sep 2006 Posts: 12,644

Quote:

Originally Posted by suzzer99

Right but this is probably the simplest.

Code:

/** Console.log out 0-4 inside the timeout */
for(i=0;i<5;i++) {
  window.setTimeout(function(index) {
    console.log(index)
  }, i * 100, i)
}

Doesn't work in IE8 though. Does work in IE10 and up. Not sure about IE9.

My googling says that it only works in IE10+. That is why the .bind approach is better. The only requirement for it to work is .bind is present (which I expect it would be on every browser including the most ancient ones).

Quote

09-12-2018 , 09:50 PM

#35195

microbet

Solar Powered

Join Date: Jan 2005 Posts: 56,488

This is probably dumb, but I didn't know bind or about the scope of let and was trying to figure a different way. Dunno if it had to be in a for loop. But, this also seems to work:

Code:

/** Console.log out 0-4 inside the timeout */
i = 0;
window.setTimeout(function() {
        while (i<5) {
                window.setTimeout(console.log(i), i * 100);
                i++;
        }
}, i * 100);

Quote

09-12-2018 , 10:35 PM

#35196

Craggoo

banned

Join Date: Sep 2006 Posts: 12,644

Quote:

Originally Posted by microbet

This is probably dumb, but I didn't know bind or about the scope of let and was trying to figure a different way. Dunno if it had to be in a for loop. But, this also seems to work:

Code:

/** Console.log out 0-4 inside the timeout */
i = 0;
window.setTimeout(function() {
        while (i<5) {
                window.setTimeout(console.log(i), i * 100);
                i++;
        }
}, i * 100);

I'm really surprised that

Code:

window.setTimeout

doesn't complain when you pass it anything other than a function as the first argument.

Quote

09-13-2018 , 01:07 AM

#35197

microbet

Solar Powered

Join Date: Jan 2005 Posts: 56,488

I was listening to a podcast and they were talking about promises. I did this on my phone. It did

0
1
2
3

I think the 4 should come but the thing I was using cut off the output at 4 lines.

Code:

for (i=0;i<5;i++) {
    var promise1 = new Promise(function(resolve, reject) {
        setTimeout(resolve(i), i*100);
        promise1.then((successMessage) => {
          console.log(successMessage);
        });     
     });
  }

Quote

09-13-2018 , 03:19 AM

#35198

microbet

Solar Powered

Join Date: Jan 2005 Posts: 56,488

I got home and tried it on my computer and it didn't get the 4. You have to set i<6 to get the 4. It's always 1 less. If you say i<60, it goes to 58. The last time through the for loop it doesn't output.

Quote

09-13-2018 , 05:05 AM

#35199

Larry Legend

Celtic Pride

Join Date: Jul 2009 Posts: 42,920

I've seen and used this interview question a lot so if I was being cheeky and the question was to do it as "fast as I could" I would do:

Quote:

/** Console.log out 0-4 inside the timeout */
for (let i=0;i<5;i++) {
window.setTimeout(function() {
console.log(i)
}, i * 100)
}

But then in modern browsers you could do:

Quote:

var myFunc = function(i) {
console.log(i)
}

for (i=0;i<5;i++) {
window.setTimeout(myFunc(i), i * 100)
}

In node you would do:

Quote:

var myFunc = function(int) {
return function() {
console.log(int)
}
}

for (i=0;i<5;i++) {
setTimeout(myFunc(i), i * 100)
}

There are fancier ways to do it but I feel like those would be enough.

Quote:

/** Given an element and a callback, traverse an element and its children (and children's children [recursion]) calling the callback on each element with the element itself as the sole argument. */
function traverse(element, callback) {}

This is very similar to an interview question I had for my current job. Traverse an object of unknown complexity and length and then the interviewer added a few changing requirements. Ternary because why not?

Quote:

var traverseElements = function(element, callback) {
element.children ? traverseElements(element.children, callback) : callback(element)
}

Quote

09-13-2018 , 05:30 AM

#35200

Larry Legend

Celtic Pride

Join Date: Jul 2009 Posts: 42,920

Quote:

Originally Posted by microbet

I was listening to a podcast and they were talking about promises. I did this on my phone. It did

0
1
2
3

I think the 4 should come but the thing I was using cut off the output at 4 lines.

Code:

for (i=0;i<5;i++) {
    var promise1 = new Promise(function(resolve, reject) {
        setTimeout(resolve(i), i*100);
        promise1.then((successMessage) => {
          console.log(successMessage);
        });     
     });
  }

If you move your promise1.then outside of the definition of the promise, then you get 0-4:

Code:

for (i=0;i<5;i++) {
    var promise1 = new Promise(function(resolve, reject) {
      setTimeout(resolve(i), i*100);
    });     
    promise1.then((successMessage) => {
      console.log(successMessage);
    });
}

Quote

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