Underscore.js is a JavaScript library that makes operations on arrays, string, objects much easier and handy. The _.constant() function is used to create a function that returns the parameter given to it. It is almost same as _.identity() function.
Note: It is very necessary to link the underscore CDN before going and using underscore functions in the browser. When linking the underscore.js CDN, the “_” is attached to the browser as global variable.
Syntax:
_.constant( object );
Parameters: This function accepts single parameter object.
Return Value: This function returns the parameter as given to the function.
Below examples illustrate the _.constant() function in Underscore.js:
Example 1:
<!DOCTYPE html>
<html>
<head>
<script src=
</script>
</head>
<body>
<script>
let str = "geeksforgeeks"
// _.constant function of underscore.js
let strFunc = _.constant(str);
console.log(`original str is: ${str}`)
console.log(`str Function is: ${strFunc}`)
// This will return true
console.log(str === strFunc())
// Both strings are exactly same
console.log("from str : ", str,
" from strFunc: ", strFunc());
</script>
</body>
</html>
|
Output:
Example 2:
<!DOCTYPE html>
<html>
<head>
<script src=
</script>
</head>
<body>
<script>
// Creating a object
let obj = {
"a": "one",
"b": "two",
"c": "three"
}
// _.constant function of underscore.js
let objFunc = _.constant(obj);
console.log(`original object is: ${obj}`)
console.log(`object Function is: ${objFunc}`)
// This will return true
console.log(obj === objFunc())
// Both objects are exactly same
console.log("from obj : ", obj.a,
" from objFunc: ", objFunc().a);
// Made Changes in object
obj.a = 12
// Change in one object reflects
// in another
console.log("change in one object "
+ "reflects in another =>")
console.log("from obj : ", obj.a,
" from objFunc: ", objFunc().a);
</script>
</body>
</html>
|
Output:
