Editing Signum Function (all)

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Preparation code

Preparation code HTML (this will be inserted in the <body> of a valid HTML5 document in standards mode) (useful when testing DOM operations or including libraries)

Include JavaScript libraries as follows: <script src="//cdn.ext/library.js"></script>

Define setup for all tests (variables, functions, arrays or other objects that will be used in the tests) (runs before each clocked test loop, outside of the timed code region) (e.g. define local test variables, reset global variables, clear canvas, etc.) (see FAQ)

// OUR TEST CODE (see other versions)
function test(sign) {
  sign(1)                  // +1
  sign(1908235)            // +1
  sign(-.1e-1)             // -1
  sign(Math.random()*2-1)  // ??
  sign(0)                  //  0
  sign(0.00000)            //  0
  sign(+Infinity)          // +1
  sign(-Infinity)          // -1
  sign(NaN)                //  0 or NaN

// other types
  sign("0")
  sign("")
  sign([])
  sign("+23")
  sign(null)
  sign(undefined)
}

// 1. Obvious and fast
function sign1 (x) { return x > 0 ? 1 : x < 0 ? -1 : 0; }

// 1.1 Modification from kbec - one type cast less, more performant, shorter
function sign1b(x) { return x ? x < 0 ? -1 : 1 : 0; }

// 2. Elegant, short, not so fast
function sign2 (x) { return x && x / Math.abs(x); }
// (some issues with several cases, see answer.)

Title

Async (check if this is an asynchronous test)

Code

test(sign4)