Lodash _.once() method of Function in lodash is used to create a function that calls the func parameter of this method only once. However, repeated calls to this function will return the value returned in the first call.
Note:
The function parameter of this method is called with this binding along with the arguments of the created function.
Syntax:
_.once(func);Parameters:
This method accepts a single parameter which is described below:
- func: It is the function that is to be restricted.
Return Value:
- This method returns the new restricted function.
Example 1: In this example, the hold is called multiple times but only the value of the first call is returned as you can call func only once as stated above.
// Requiring lodash library
const _ = require('lodash');
// Calling once() method with its parameter
let hold = _.once(function (trap) {
console.log(trap + '!');
});
// Calling hold multiple times
hold('Logged in to the console');
hold('GfG');
hold('CS');
Output:
Logged in to the console!Example 2: In this example, each time the fetch is called the same value is returned as returned to the first call.
// Requiring lodash library
const _ = require('lodash');
// Calling once() method with its parameter
let fetch = _.once(function (value) {
return value;
});
// Calling fetch multiple times
console.log(fetch(1013));
console.log(fetch(1014));
Output:
1013
1013