How do I know an array contains all zero(0) in Javascript

You can use either Array.prototype.every or Array.prototype.some.

Array.prototype.every

With every, you are going to check every array position and check it to be zero:

const arr = [0,0,0,0];
const isAllZero = arr.every(item => item === 0);

This has the advantage of being very clear and easy to understand, but it needs to iterate over the whole array to return the result.

Array.prototype.some

If, instead, we inverse the question, and we ask "does this array contain anything different than zero?" then we can use some:

const arr = [0,0,0,0];
const someIsNotZero = arr.some(item => item !== 0);
const isAllZero = !someIsNotZero; // <= this is your result

This has the advantage of not needing to check the whole array, since, as soon it finds a non-zero value, it will instantly return the result.

for loop

If you don't have access to modern JavaScript, you can use a for loop:

var isAllZero = true;

for(i = 0; i < myArray.length; ++i) {
  if(myArray[i] !== 0) {
    isAllZero = false;
    break;
  }
}

// `isAllZero` contains your result

RegExp

If you want a non-loop solution, based on the not-working one of @epascarello:

var arr  = [0,0,0,"",0],
    arrj = arr.join('');
if((/[^0]/).exec(arrj) || arr.length != arrj.length){
    alert('all are not zero');
} else {
    alert('all zero');
}

This will return "all zero" if the array contains only 0

Using ECMA5 every

function zeroTest(element) {
  return element === 0;
}

var array = [0, 0, 0, 0];
var allZeros = array.every(zeroTest);

console.log(allZeros);

array = [0, 0, 0, 1];
allZeros = array.every(zeroTest);

console.log(allZeros);

Use an early return instead of 2, 3 jumps. This will reduce the complexity. Also we can avoid initialisation of a temp variable.

function ifAnyNonZero (array) {
  for(var i = 0; i < array.length; ++i) {
    if(array[i] !== 0) {
      return true;
    }
  }
  return false;
}