forEach Method (Map) (JavaScript)

Performs the specified action for each element in a map.

Syntax

mapObj.forEach(callbackfn[, thisArg])  

Parameters

mapObj
Required. A Map object.

callbackfn
Required. The function that forEach calls one time for each element in the map. callbackfn accepts up to three arguments. forEach calls the callbackfn function one time for each element in the map.

thisArg
Optional. An object that the this keyword can refer to in the callbackfn function. If thisArg is omitted, undefined is used as the this value.

Exceptions

If the callbackfn argument is not a function object, a TypeError exception is thrown.

Remarks

The syntax of the callback function is as follows:

function callbackfn(value, key, mapObj)

You can declare the callback function by using up to three parameters, as shown in the following table.

Callback argument Definition
value A value contained in the map.
key A key contained in the map.
mapObj The Map object to traverse.

Example

The following example shows how to retrieve members of a Map using forEach.

var m = new Map();  
m.set(1, "black");  
m.set(2, "red");  
m.set("colors", 2);  
m.set({x:1}, 3);  

m.forEach(function (item, key, mapObj) {  
    document.write(item.toString() + "<br />");  
});  

document.write("<br />");  
document.write(m.get(2));  

// Output:  
// black  
// red  
// 2  
// 3  
//  
// red  

Requirements

Supported in the Internet Explorer 11 standards document mode. Also supported in Store apps (Windows 8.1 and Windows Phone 8.1). See Version Information.
Not supported in the following document modes: Quirks, Internet Explorer 6 standards, Internet Explorer 7 standards, Internet Explorer 8 standards, Internet Explorer 9 standards, Internet Explorer 10 standards. Not supported in Windows 8.