Info

Derived from this question on StackOverflow: Number.sign() in JavaScript

Versions of the test: test everything — only numbers — only integers

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Preparation code

 
<script>
  Benchmark.prototype.setup = function() {
    // 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
    }
    
    
    // 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.)
    
    // 3. The art... but very slow
    function sign3 (x) { return (x > 0) - (x < 0); }
    
    
    // 4. Type-safe:
    function sign4 (x) {
        return typeof x == 'number' ? x ? x < 0 ? -1 : 1 : isNaN(x) ? NaN : 0 : NaN;
    }
  };
</script>

Test runner

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test(sign1)

test(sign1b)

test(sign2)

test(sign3)

test(sign4)

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