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JavaScript Map forEach() Method

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JavaScript Map.forEach method is used to loop over the map with the given function and executes the given function over each key-value pair.

Syntax:

myMap.forEach(callback, value, key, thisArg)

Parameters: This method accepts four parameters as mentioned above and described below:

  • callback: This is the function that executes on each function call.
  • value: This is the value for each iteration.
  • key: This is the key to reach iteration.
  • thisArg: This is the value to use as this when executing callback.

Returns: It returns the undefined value.

Example 1: In this example, The forEach method is used to log each key-value pair to the console.

Javascript

// Creating a map using Map object
let mp = new Map()
 
// Adding values to the map
mp.set("a", 1);
mp.set("b", 2);
mp.set("c", 3);
 
// Logging map object to console
mp.forEach((values, keys) => {
    console.log(values, keys)
})

                    

Output: 

1a
2b
3c

Example 2: In this example, the forEach method is employed to iterate through the map, printing each key-value pair to the console in the format “values: [value], keys: [key]”.

Javascript

// Creating a map using Map object
let mp = new Map()
 
// Adding values to the map
mp.set("a", 65);
mp.set("b", 66);
mp.set("c", 67);
mp.set("d", 68);
mp.set("e", 69);
mp.set("f", 70);
 
// Logging map object
console.log(mp);
mp.forEach((values, keys) => {
    console.log("values: ", values +
        ", keys: ", keys)
})

                    

Output: 

[object Map]
values: 65, keys: a
values: 66, keys: b
values: 67, keys: c
values: 68, keys: d
values: 69, keys: e
values: 70, keys: f

Example 3: This example shows the basic use of the JavaScript Map.forEach() method.

Javascript

let mp = new Map();
 
// adding values to the map
mp.set("a", 65);
mp.set("b", 66);
mp.set("c", 67);
mp.set("d", 68);
mp.set("e", 69);
mp.set("f", 70);
 
// logging map object to console
console.log(mp);
 
// logging concatenated keys and values
mp.forEach((value, key) => {
  console.log(key+": " + value);
});

                    

Output
Map(6) {
  'a' => 65,
  'b' => 66,
  'c' => 67,
  'd' => 68,
  'e' => 69,
  'f' => 70
}
a: 65
b: 66
c: 67
d: 68
e: 69
f: 70

We have a complete list of Javascript Map Methods, to check those please go through Javascript Map Complete Reference article.

Browsers Supported: 

  • Google Chrome 38 and above
  • Microsoft Edge 12 and above
  • Mozilla Firefox 25 and above
  • Internet Explorer 11 and above
  • Safari 8 and above
  • Opera 25 and above


Last Updated : 04 Dec, 2023
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