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Collect.js | when() Function
  • Last Updated : 10 Jun, 2020

The when() function is used to callback if the first argument in the given proves to be true. In JavaScript, the array is first converted to a collection and then the function is applied to the collection.
Syntax: 

data.when(conditional ,rule)

Parameters: This function accept two parameters as mentioned above and described below:

  • rule:  This parameter holds the operation rule or the condition to be applied on the collection. 
  • conditional:  This parameter holds the conditional value true or false.  
     

Return value :  Return the modified collection list.
 

Below examples illustrate the when() function in collect.js:
Example 1: Here in this example, we take a collection and then using the when() function modify the collection.

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// It is used to import collect.js library   
const collect = require('collect.js');
  
const collection = collect([0 , 1 , 2]);
collection.when(true, items => items.push(3));
  
console.log(collection.all());

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Output: 

[0 , 1 , 2 , 3]

Example 2: Same as above example but applying a different operation to perform.

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// It is used to import collect.js library   
const collect = require('collect.js');
  
const collection = collect([0 , 1 , 2]);
collection.when(true, items => items.put('Jason'));
  
console.log(collection.all());

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Output: 

[ 0, 1, 2, Jason: undefined ]

Reference: https://collect.js.org/api/when.html

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