Array.prototype.includes() – JavaScript – MDN Web Docs


ES2016 feature: `Array.prototype.includes`

`Array.prototype.includes` is an ECMAScript proposal by Domenic Denicola and Rick Waldron. It is at stage 4 (finished) and part of ECMAScript 2016.

javascript – Array.prototype.includes vs. Array.prototype

Conceptually you should use indexOf when you want to use the position indexOf just give you to extract the value or operate over the array, i.e using slice, shift or split after you got the position of the element.

tl;dr: NaN is treated differently: [NaN].indexOf(NaN) > -1 is false [NaN].includes(NaN) is true From the proposal : Motivation When using ECMAScript arrays, it is commonly desired to determine if the array includes an element. The prevailing pattern for this is if (arr.indexOf(el) !== -1) {

with various other possibilities, e.g. arr.indexOf(el) >= 0 , or even ~arr.indexOf(el) . These patterns exhibit two problems: They fail to «say what you mean»: instead of asking about whether the array includes an element, you ask what the index of the first occurrence of that element in the array is, and then compare it or bit-twiddle it, to determine the answer to your actual question. They fail for NaN , as indexOf uses Strict Equality Comparison and thus [NaN].indexOf(NaN) === -1 . Proposed Solution We propose the addition of an Array.prototype.includes method, such that the above patterns can be rewritten as if (arr.includes(el)) {

This has almost the same semantics as the above, except that it uses the SameValueZero comparison algorithm instead of Strict Equality Comparison, thus making [NaN].includes(NaN) true. Thus, this proposal solves both problems seen in existing code. We additionally add a fromIndex parameter, similar to Array.prototype.indexOf and String.prototype.includes , for consistency. Further information: SameValueZero algorithm Strict Equality Comparison algorithmBest answer · 95
If you wonder about performances, for the moment, indexOf is faster, but this JSperf test tend to show that more the time pass, more includes() will be faster than indexOf (i guess it will be optimized further). IMHO, i also prefer to write if (arr.includes(el)) {} since it is clearer and more maintainable than if (arr.indexOf(el) !== -1) {}5Conceptually you should use indexOf when you want to use the position indexOf just give you to extract the value or operate over the array, i.e using slice, shift or split after you got the position of the element. On the other hand, Use Array.includes only to know if the value is inside the array and not the position because you don’t care about it.

Difference Between indexOf and findIndex function of array
performance – Why is looping through an Array so much

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GitHub – tc39/Array.prototype.includes: Spec, tests

SameValueZero is generally the better choice, as it allows you to detect if an array includes a NaN. The argument for Strict Equality Comparison boils down to «bug compatibility» with Array.prototype.indexOf. But one of the purposes of Array.prototype.includes is …

Array.prototype.includes() sample3 –

HTML preprocessors can make writing HTML more powerful or convenient. For instance, Markdown is designed to be easier to write and read for text documents and you could write a loop in Pug. To get the best cross-browser support, it is a common practice to apply vendor prefixes to CSS properties and

GitHub – ljharb/array-includes: Array.prototype.includes

Because Array.prototype.includes depends on a receiver (the this value), the main export takes the array to operate on as the first argument. Getting started npm install –save array-includes

3. Array.prototype.includes – Exploring JS: JavaScript

Isn’t that inconsistent w.r.t. Array.prototype.includes? If Array includes worked exactly like string includes , it would accept arrays, not single elements. But the two includes follow the example of indexOf ; characters are seen as a special case and strings with arbitrary lengths as the general case.

ECMAScript 2016: Array.prototype.includes | Marius Schulz

ECMAScript 2016: Array.prototype.includes. February 3, 2016. One of the two features that will be part of ECMAScript 2016 is the new Array.prototype.includes method. It determines whether an array contains a certain element and returns either true or false.

Array.prototype.includes – GitHub

Array.prototype.includes 1 Array.prototype.includes ( searchElement [ , fromIndex ] ) # Note 1. includes compares searchElement to the elements of the array, in ascending order, using the SameValueZero algorithm, and if found at any position, returns true; otherwise, false is returned.

JavaScript Array prototype Constructor – W3Schools

The prototype constructor allows you to add new properties and methods to the Array() object. When constructing a property, ALL arrays will be given the property, and its value, as default. When constructing a method, ALL arrays will have this method available. Note: Array.prototype does not refer to a single array, but to the Array() object

Array.prototype.includes() – JavaScript | MDN

includes() 方法用来判断一个数组是否包含一个指定的值,根据情况,如果包含则返回 true,否则返回false。 The source for this interactive example is stored in a GitHub repository. If you’d like to contribute to the interactive examples project, please clone https

Introducing the new features that ECMAScript 2016 (ES7

Array.prototype.includes() checks the array for the value passed as an argument. It returns true if the array contains the value , otherwise, it returns false . Before, we needed to use Array.prototype.indexOf() to check if the given array contains an element or not.

Node.js: «Array.includes is not a function» error – reddit

I’m fairly new to node.js and I wrote a code to check if an element is included in some other array variable. I’ve used the function Array.includes but node.js is not recognizing it. I’ve put the same code in my Chrome’s console and it works just fine.

1069063 – Implement Array.prototype.includes – Mozilla

Shared components used by Firefox and other Mozilla software, including handling of Web content; Gecko, HTML, CSS, layout, DOM, scripts, images, networking, etc. Issues with web page layout probably go here, while Firefox user interface issues belong in the Firefox product.