CODEWITHSUNDEEP
javascript
user1234
user1234

Reputation: 3159

combine multiple && conditions into 1

Is there a better way in Javascript to do null check on multiple elements I want to 

a=null; b=null;....n=null;

So in total I have 14 variables set to null initially and I want to apply just one solution to all of them if they are ```null``.

if (a=== null && b=== null&& c=== null&& d=== null&& e=== null &&...&& n===null){
// set some field to false
}

is there a better way to check for null, as this may get cumbersome if we have more arrays added Thanks!

Upvotes: 0

Views: 303

Answers (2)

Ori Drori
Ori Drori

Reputation: 191976

Create a an array of arrays, iterate it using Array.every(), and do something if all item values are null: 

if([a, b, c, ... n].every(a => a === null)) {
    // set some field to false
}

Upvotes: 3

J.Ko
J.Ko

Reputation: 1052

If you're new to JS, in JS, values can be "falsey" or "truthy". if / while / for will run if the value it's supposed to evaluates to "truthy." There are few "falsey" values in JS, and the rest are considered "truthy." The false values are:

  • undefined
  • 0
  • NaN
  • null
  • ''
  • false

(I believe I got them all. Think of "six sins": there are six of these)

So check the following code, and what their outcomes are:

if(0) console.log('yay') // won't run
if(false) console.log('yay') // won't run
if(null) console.log('yay') // won't run
if('') console.log('yay') // won't run
if(NaN) console.log('yay') // won't run


if([]) console.log('yay') // will run
if('0') console.log('yay') // will run

This is a long winded way of saying if you want to do something based on whether array is empty or not, try the following:

let arr = [1,2,3,4]
if(arr.length){
  //do stuff if array is not empty
} else {
   // do stuff if array is empty
}

Now to actually solve the problem for you, do the following:

const masterArray = [a, b, c, d, ... , n];
let length = 0;
masterArray.forEach(subarr=>{
  length += subarr.length;
})

//At this point, if no array had any elements, length would be 0
if(length === 0){
  // do stuff
}

Upvotes: 1

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