3. some and every #

Created Thursday 25 March 2021

• Purpose - concise code.
• Given a criteria and an array, there are 3 possibilities. The criteria holds for:
  1. every element
  2. some element
  3. no element - same as not(for all). Duplicate of 2.
• Consquently, JS has two array methods:
  1. every
  2. some
• About the functions:
  • Syntax: myArray.every(criteriaFunc(ele, idx){}). Similarly for some.
  • You can access index as the 2nd param.
  • Working: every stops at first violation. some stops at first validation.
  • Time complexity - Θ(n)
  • Both return Boolean.

Example

let nums = [22, 82, 90, 3, 96];

function isEven(a) {	return a%2==0;	}
console.log('All even - ' + nums.every(isEven));
/* output
All even - false
*/

console.log('Atleast one even - ' + nums.some(isEven));
/* output
Atleast one even - true
*/

// Access index
let nums = [22, 82, 90, 19, 96];

console.log(nums.some((a, b) => {
	if(a%2)
		return false;
	console.log(b);
	return true;
}));

/* output
true
3
*/