Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

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

Posted by Daniel Benisti
.a{fill-rule:evenodd;}techdegree seal-36
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

Gemini Brain
Gemini Brain
13,817 Points
Gemini Brain
Gemini Brain
13,817 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;
}