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How to check if all values in array are false in JavaScript?

To check if all values in array are false, use the array every() method. The every() method iterates over the array and compares each element to false. If all array elements are false, then the every() method will return true; otherwise, it will return false.

let arr1 = [false, false, false];
let arr2 = [true, false, false, true];

let result = arr1.every(element => element === false);
console.log(result); //true

result = arr2.every(element => element === false);
console.log(result); //false

The explanation of the code is as follows:

The every() method calls a callback function for each element of the array. Inside the callback function, you specify the condition (element === false). If any one of the array elements does not satisfy the condition, then the every() method short-circuits and returns false.

You can even use for...of loop to check if all values in array are false.

let arr1 = [false, false, false];
let arr2 = [true, false, false, true];

let result = true;
for(let element of arr1){
  if(element === true){
    result = false;
    break;
  }
}
console.log(result); //true

result = true;
for(let element of arr2){
  if(element !== false){
    result = false;
    break;
  }
}
console.log(result); //false

If you are interested in checking if all values in the array are falsy, then you can use the same every() method. In JavaScript, there are six falsy values: false, null, undefined, NaN, "" (empty string), and 0. All other values except falsy are truthy.

let arr1 = [27, "JavaScript", true];
let arr2 = [0, undefined, ""];

let result = arr1.every(element => !element);
console.log(result); //false

result = arr2.every(element => !element);
console.log(result); //true