{

How to check boolean value of an array in javascript


In this blog post, You’ll learn to check the boolean value of an array in javascript or typescript.

Find Array contains a boolean value in javascript

The array contains a collection of similar type values.

For example, we have a User form that contains multiple checkboxes - which can have select All/Deselect All in Angular application,

A checkbox in FormGroup is defined with FormArray which holds true - if the checkbox is checked, false - checkbox is not checked.

To implement form validation like if a user is not checked any checkbox, display error message - Please check at least one checkbox.

Then how do we check the boolean value true that exists in the array of checkboxes in Angular,

This post talks about multiple ways of checking true/false values, that exist in an Array in Javascript/Typescript/Angular.

  • For loop with if block
  • Array some() method
  • Array indexOf method
  • Es7 Array Includes

All the examples will work in Javascript, typescript, and Angular.

For loop with if block example

A basic developer will use the below logic to check the true value in an array

  • Iterate the array used for the normal loop
  • Check each element for true value using if the loop
  • if found, return true and break from the loop
  • if not found, return a false value
function checkTrueExistsArray(array){
for(var k=0; k<array.length; k++){
    if(array[k]){
        return true
        break;
    }
}
return false;
}
var arrayVariable= [false,false,true,false,true]
var arrayVariable1= [false,false,false,false,false]

console.log(checkTrueExistsArray(arrayVariable)) //true
console.log(checkTrueExistsArray(arrayVariable1)) //false

Array Some() method

Some() in an Array is an inbuilt method in javascript language.

  • It iterates each element and calls the callback for each value,
  • if the callback returns a true value, stop the iteration and returns true
  • if the callback returns a false value, iteration goes to the next iteration until it returns true or array iteration is done.
function checkTrueUsingArraySome(array){
  if(array.some((item)=> item === true)){
    return true;
    }
    return false;
}
var arrayVariable= [false,false,true,false,true]
var arrayVariable1= [false,false,false,false,false]
console.log(checkTrueUsingArraySome(arrayVariable)) //true
console.log(checkTrueUsingArraySome(arrayVariable1)) //false

Array indexOf method example

indexOf method in Array accepts input parameters, returns index position if input found in an array, else returns -1

function checkTrueUsingArrayIndexOf(array){
  if(array.indexOf(true) != -1){
    return true;
    }
    return false;
}
var arrayVariable= [false,false,true,false,true]
var arrayVariable1= [false,false,false,false,false]

console.log(checkTrueUsingArrayIndexOf(arrayVariable)) //true
console.log(checkTrueUsingArrayIndexOf(arrayVariable1)) //false

Es7 Includes checking true value

ES7 i.e latest javascript language introduced includes method

It returns true if the value found in an array else returns false, You can check more about es7 includes

function checkTrueUsingArrayInclude(array){
  if(array.includes(true)){
    return true;
    }
    return false;
}
var arrayVariable= [false,false,true,false,true]
var arrayVariable1= [false,false,false,false,false]

console.log(checkTrueUsingArrayInclude(arrayVariable)) //true
console.log(checkTrueUsingArrayInclude(arrayVariable1)) //false
THE BEST NEWSLETTER ANYWHERE
Join 6,000 subscribers and get a daily digest of full stack tutorials delivered to your inbox directly.No spam ever. Unsubscribe any time.

Similar Posts
Subscribe
You'll get a notification every time a post gets published here.