NodeList.prototype.forEach() - Web APIs 编辑

The forEach() method of the NodeList interface calls the callback given in parameter once for each value pair in the list, in insertion order.

Syntax

someNodeList.forEach(callback[, thisArg]);

Parameters

callback

A function to execute on each element of someNodeList. It accepts 3 parameters:

currentValue

The current element being processed in someNodeList.

currentIndex Optional

The index of the currentValue being processed in someNodeList.

listObj Optional

The someNodeList that forEach() is being applied to.

thisArg Optional

Value to use as this when executing callback.

Return value

undefined.

Example

let node = document.createElement("div");
let kid1 = document.createElement("p");
let kid2 = document.createTextNode("hey");
let kid3 = document.createElement("span");

node.appendChild(kid1);
node.appendChild(kid2);
node.appendChild(kid3);

let list = node.childNodes;

list.forEach(
  function(currentValue, currentIndex, listObj) {
    console.log(currentValue + ', ' + currentIndex + ', ' + this);
  },
  'myThisArg'
);

The above code results in the following:

[object HTMLParagraphElement], 0, myThisArg
[object Text], 1, myThisArg
[object HTMLSpanElement], 2, myThisArg

Polyfill

This polyfill adds compatibility to all Browsers supporting ES5:

if (window.NodeList && !NodeList.prototype.forEach) {
    NodeList.prototype.forEach = function (callback, thisArg) {
        thisArg = thisArg || window;
        for (var i = 0; i < this.length; i++) {
            callback.call(thisArg, this[i], i, this);
        }
    };
}

OR

if (window.NodeList && !NodeList.prototype.forEach) {
   NodeList.prototype.forEach = Array.prototype.forEach;
}

The above behavior is how many browsers actually implement NodeList.prototype.forEach() (Chrome, for example).

Specifications

Browser Compatibility

BCD tables only load in the browser

See also

• Node
• NodeList