JavaScript Insert Key-Value Pair in Map
To insert a new key-value pair to a Map in JavaScript, call set() method on this Map and pass the key and value as arguments.
Syntax
The syntax to insert a new key-value pair into a Map map
is
map.set(key, value)
Examples
In the following example, we create an empty map, and insert some key-value pairs into it using set() method.
index.html
<!DOCTYPE html> <html lang="en"> <body> <pre id="output"></pre> <script> var map1 = new Map(); map1.set('a', 10); map1.set('b', 20); var displayOutput = ''; map1.forEach (function(value, key) { displayOutput += key + ' - ' + value + '\n'; }); document.getElementById('output').innerHTML += displayOutput; </script> </body> </html>
If the key already exists, then the value is updated with the new value.
index.html
<!DOCTYPE html> <html lang="en"> <body> <pre id="output"></pre> <script> var map1 = new Map([ ['a', 10], ['b', 20] ]); map1.set('a', 88); var displayOutput = ''; map1.forEach (function(value, key) { displayOutput += key + ' - ' + value + '\n'; }); document.getElementById('output').innerHTML += displayOutput; </script> </body> </html>
Conclusion
In this JavaScript Tutorial, we learned how to insert a new key-value pair into a Map in JavaScript using set() method, with examples.