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JavaScript JavaScript Arrays Store Multiple Values in an Array Copy and Combine Arrays with the Spread Operator

Posted by Daniel Benisti
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Daniel Benisti
Front End Web Development Techdegree Graduate 22,224 Points

how the spread operator Math.max/Math.min iterate over the elements? (on minute 7:10)

Hey everyone! i'm trying to understand the login here. so we pass the numbers to the Math.max method as a spread array. how does the method loops over the elements?

1 Answer

Martin Ulč
Martin Ulč
15,396 Points
Martin Ulč
Martin Ulč
15,396 Points

Hi, Math.max/Math.min functions naturally expect an array of numbers. Exact definition of these functions is the following:

min(...values: number[]): number;
max(...values: number[]): number;

You can also read more here:

min: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/min

max: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/max

But if you are interested in the way how these inbuilt functions actually works I found for example Chrome V8 Engine code. Hope it will help you understand.

// ECMA 262 - 15.8.2.11
function MathMax(arg1, arg2) {  // length == 2
  var length = %_ArgumentsLength();
  if (length == 2) {
    arg1 = TO_NUMBER(arg1);
    arg2 = TO_NUMBER(arg2);
    if (arg2 > arg1) return arg2;
    if (arg1 > arg2) return arg1;
    if (arg1 == arg2) {
      // Make sure -0 is considered less than +0.
      return (arg1 === 0 && %_IsMinusZero(arg1)) ? arg2 : arg1;
    }
    // All comparisons failed, one of the arguments must be NaN.
    return NaN;
  }
  var r = -INFINITY;
  for (var i = 0; i < length; i++) {
    var n = %_Arguments(i);
    n = TO_NUMBER(n);
    // Make sure +0 is considered greater than -0.
    if (NUMBER_IS_NAN(n) || n > r || (r === 0 && n === 0 && %_IsMinusZero(r))) {
      r = n;
    }
  }
  return r;
}

// ECMA 262 - 15.8.2.12
function MathMin(arg1, arg2) {  // length == 2
  var length = %_ArgumentsLength();
  if (length == 2) {
    arg1 = TO_NUMBER(arg1);
    arg2 = TO_NUMBER(arg2);
    if (arg2 > arg1) return arg1;
    if (arg1 > arg2) return arg2;
    if (arg1 == arg2) {
      // Make sure -0 is considered less than +0.
      return (arg1 === 0 && %_IsMinusZero(arg1)) ? arg1 : arg2;
    }
    // All comparisons failed, one of the arguments must be NaN.
    return NaN;
  }
  var r = INFINITY;
  for (var i = 0; i < length; i++) {
    var n = %_Arguments(i);
    n = TO_NUMBER(n);
    // Make sure -0 is considered less than +0.
    if (NUMBER_IS_NAN(n) || n < r || (r === 0 && n === 0 && %_IsMinusZero(n))) {
      r = n;
    }
  }
  return r;
}