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This article mainly explains "how to use foreach () in es6". Interested friends may wish to have a look at it. The method introduced in this paper is simple, fast and practical. Let's let the editor learn how to use foreach () in es6.

In es6, the foreach () method is used to traverse the array, calling each element of the array, and passing the element to the callback function for processing, with the syntax "array.forEach (function (currentValue,index,arr), thisValue)".

The operating environment of this tutorial: windows7 system, ECMAScript version 6, Dell G3 computer.

In es6, the foreach () method is used to traverse the array, calling each element of the array, and passing the element to the callback function for processing. The details are as follows:

Array.forEach (function (currentValue, index, arr), thisValue) parameter description function (currentValue, index, arr) is required. The function to be called for each element in the array.

Function parameters: parameter description currentValue is required. The current element index is optional. The index value of the current element. Arr is optional. The array object to which the current element belongs. ThisValue is optional. The value passed to the function usually uses the "this" value.

If this parameter is empty, "undefined" is passed to the "this" value.

For each element that appears in the array, the forEach method calls the callbackfn function once, in ascending indexing order, but does not call the callback function for the array's empty elements.

In addition to array objects, the forEach method can also be used for any object that has a length property and has a numerically indexed property name, such as associative array objects, Arguments, and so on.

The forEach method does not directly modify the original array, but the callback function may modify it. The result of modifying the array object after the forEach method starts is shown in the table.

The callback function modifies the influence of the array whether the conditional element after the forEach method starts is passed to the callback function to add an element beyond the original length of the array No add an element to fill the missing element in the array is, if the index has not been passed to the callback function element has been changed, if the element has not been passed to the callback function to remove the element from the array, unless the element has been passed to the callback function

Example 1

The following example iterates over the array a using forEach, and then displays the value and subscript index output of each element, as follows:

Function f (value,index,array) {console.log ("a [" + index + "] =" + value);} var a = ['a', 'baked,' c']; a.forEach (f)

The results of the demonstration are as follows:

Example 2

The following example iterates over the array a using forEach, then calculates the sum of the array elements and outputs.

Var a = [10,11,12], sum = 0boma.forEach (function (value) {sum + = value;}); console.log (sum); / / return 33

Example 3

The following example shows how to use the second parameter of the forEach () method, which is passed to the this of the callback function. When iterating over an array, first read the value of the array element, and then overwrite its value.

Var obj = {F1: function (value,index,array) {console.log ("a [" + index + "] =" + value); arrar [index] = this.f2 (value);}, f2: function (x) {return x * x;}}; var a = [12,26,36]; a.forEach (obj.f1, obj); console.log (a) / / return [144676, 1296] to this point, I believe you have a better understanding of "how to use foreach () in es6". You might as well do it in practice. Here is the website, more related content can enter the relevant channels to inquire, follow us, continue to learn!

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