for in / for of – Beau teaches JavaScript



For… in and for… of loops allow you to loop through property names and values in JavaScript.

🔗 Code: http://codepen.io/beaucarnes/pen/oBKWLq?editors=0012

🐦 Beau Carnes on Twitter: https://twitter.com/carnesbeau

⭐JavaScript Playlists⭐
▶JavaScript Basics: https://www.youtube.com/playlist?list=PLWKjhJtqVAbk2qRZtWSzCIN38JC_NdhW5
▶Data Structures and Algorithms: https://www.youtube.com/playlist?list=PLWKjhJtqVAbkso-IbgiiP48n-O-JQA9PJ
▶Design Patterns: https://www.youtube.com/playlist?list=PLWKjhJtqVAbnZtkAI3BqcYxKnfWn_C704
▶ES6: https://www.youtube.com/playlist?list=PLWKjhJtqVAbljtmmeS0c-CEl2LdE-eR_F
▶Clean Code: https://www.youtube.com/playlist?list=PLWKjhJtqVAbkK24EaPurzMq0-kw5U9pJh


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15 thoughts on “for in / for of – Beau teaches JavaScript

  • April 29, 2019 at 17:21
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    Wow, this is quite good! Though I think that instead of "x" the first variable name should've been "propertyName" — just to make it more explicit and thus clear what's happening. And then maybe go over the code with "x" afterwards just to show that it really doesn't matter what that first variable is called.

    Slightly more problematically, in the beginning, stating that "'for…in' will loop through property names and 'for…of' will loop through property values" can be confusing at first when compared to the later statement (beginning at around 2:15) that the former works on what is enumerable while the latter what is iterable. In that vein, finally, I also thought that the later contrast between the two was good but felt just a bit rushed somehow.

    Still, overall a nice video for us beginners; thanks!

  • April 29, 2019 at 17:21
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    "for in" loops through innumerable properties, property "names" 0:05:
    1:582:16, object defined properties
    3:12, array numeric indexes & object defined properties

    "for of" loops through iterable objects (i.e. array, map, set), property "values" 0:08:
    4:014:18, values in arrays

  • April 29, 2019 at 17:21
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    one way of remembering : 'i' n –> ob 'j' ect [look visually similar]
    so the other must be : off –> array

    OR "I want to get to know you in person " if you know that person is normally best as an object ?

  • April 29, 2019 at 17:21
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    just remember by this:
    for (let index in Arr) {
    console.log(index + Arr[index] ); //gives fname beau
    }
    for (let item of Arr) {
    console.log(item); //gives 3,5,7
    }

  • April 29, 2019 at 17:21
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    why the `for of` can't output the `foo` value of the arr? It's confusing. Do you mind to explain that a little bit explicit? Many thanks.

  • April 29, 2019 at 17:21
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    I was trying to understand this video i watched it many time but no point Then I decided to take break 30 min and come back to concentrate in last 10 video in this tuturiol and come back to this video just in one minute i find it very simple and clear new lesson today to take break after study couple of hour then come back will find everything easy, I love your video really very clear and important for everyone want to be perofessinal in JS Thank you bro

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