Push to an Array using a for loop

Question

im a JS newbie. Trying to figure out this problem below. I am stuck on the "if" statement and not sure exactly what to put in. Also im not sure if my "push" is setup right

// Define a function named `compact` that accepts an array and returns
// another array with all the falsey values removed from it. For example,
// if this array was passed in:
//   [1, 4, 0, '', undefined, false, true, null, {mj: 'mj'}, 'Hello']
// the function would return this, as a result:
//   [1, 4, true, {mj: 'mj'}, 'Hello']

var compact = function (array) {
    var truthyValues = [];
    for (var i = 0; i < array.length; i += 1) {
        if () {
            truthyValues.push[i];
        }
    }
    return truthyValues;
};

Read this - meaning of "falsy" and "truthy" values: sitepoint.com/javascript-truthy-falsy Non-Boolean values are converted to "true" or "false" when a Boolean value is needed, and how that is done depends on some rules. In other, more type-strict languages you could not do that but would be forced to declare explicitly whether you want "true" or "false". — Mörre
– Mörre, Commented Dec 6, 2013 at 20:18

Scott Mermelstein · Accepted Answer · 2013-12-06 20:17:44Z

4

You're close. Here's what the if should be:

if (array[i]) {
    truthyValues.push(array[i]);
}

Since you want to check for truthiness of each array element, just put array[i] in the if block. That gets the value of the array at i, and will evaluate as true if that value is truthy.

Then push not i - the index into array - but array[i], so that the actual value is in truthyValues.

answered Dec 6, 2013 at 20:17

Scott Mermelstein

15.4k4 gold badges51 silver badges77 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

scrblnrd3 · Accepted Answer · 2013-12-06 20:18:13Z

4

Just put the value you want to check is truthy in the if statement, since the if statement checks for truthiness.

if(array[i]){
  truthyValues.push(array[i]);
}

answered Dec 6, 2013 at 20:18

scrblnrd3

7,4449 gold badges36 silver badges65 bronze badges

Comments

C1pher · Accepted Answer · 2013-12-06 20:17:51Z

1

I think you can just use:

if (array[i]) { truthyValues.push(array[i]); }

Values like null will trigger false.

answered Dec 6, 2013 at 20:17

C1pher

1,9726 gold badges34 silver badges52 bronze badges

Comments

Jed Schneider · Accepted Answer · 2013-12-06 20:19:00Z

1

if (typeof array[i] !== "undefined" && array[i] !== null) {// push to array // }

most of these other answers will not work for falsy and existy values. You'll need to define what you intend to be existy and write a helper function for that. you could use the one I provided as a start and then roll your own.

answered Dec 6, 2013 at 20:19

Jed Schneider

14.8k4 gold badges40 silver badges47 bronze badges

4 Comments

Mörre Over a year ago

He says "falsey" (sic) so I guess the exercise is to use the t-Boolean conversions built into Javascript, so being fuzzy is deliberate here, I think. You do what a good programmer would do - be explicit :)

Jed Schneider Over a year ago

@Mörre this should help him get started with being explicit in JS: zero.milosz.ca

Mörre Over a year ago

What's "existy values"? Never heard that term before. The only occurrence on the web is your comment according to Google :)

Mörre Over a year ago

I don't find "existy" on that webpage. I don't think inventing a new word when the person asking the question already has enough to do to understand "truthy" and "falsy" is not a good idea, especially when there is no one but you using it. By the way, even the variable names in the example say "truthy" - as I said, it seems the exercise is deliberately using this JS "specialty", likely for teaching purposes.

Collectives™ on Stack Overflow

Push to an Array using a for loop

4 Answers 4

Comments

Comments

Comments

4 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

Comments

Comments

Comments

4 Comments

Your Answer

Sign up or log in

Post as a guest

Related