check if all values in array equal same javascript code example

Example 1: check array values equal js

[1,1,1,1].every( (val, i, arr) => val === arr[0] )   // true

Example 2: check if all elements in array match a condition javascript

const isBelowThreshold = (currentValue) => currentValue < 40;

const array1 = [1, 30, 39, 29, 10, 13];

console.log(array1.every(isBelowThreshold));
// expected output: true