DOMTokenList.forEach() - Web APIs 编辑

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

Syntax

tokenList.forEach(callback [, thisArg]);

Parameters

callback

Function to execute for each element, eventually taking three arguments:

currentValue

The current element being processed in the array.

currentIndex

The index of the current element being processed in the array.

listObj

The array that forEach() is being applied to.

thisArg Optional

Value to use as this when executing callback.

Return value

undefined.

Example

In the following example we retrieve the list of classes set on a <span> element as a DOMTokenList using Element.classList. We when retrieve an iterator containing the values using forEach(), writing each one to the <span>'s Node.textContent inside the forEach() inner function.

HTML

<span class="a b c"></span>

JavaScript

let span = document.querySelector("span");
let classes = span.classList;
let iterator = classes.values();

classes.forEach(
  function(value, key, listObj) {
    span.textContent += `${value} ${key}/${this}  ++  `;
  },
  "arg"
);

Result

Polyfill

This polyfill adds compatibility to all Browsers supporting ES5:

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

Specifications

Browser Compatibility

BCD tables only load in the browser

See also

• DOMSettableTokenList (object that extends DOMTokenList with settable .value property)