Javascript convert __string__ to __number__

jsconvert.md

convert a string to number at JavaScript.

1. +

   +'12';     // 12
   typeof +'12'     // number
  
   +'12s';    // NaN
   typeof +'12s';   // number

2. *

   '12' * 1;   // 12
   typeof('12' * 1);  // number
   typeof '12' * 1;   // NaN
  
   '12s' * 1   // NaN
   typeof('12s' * 1)  // number

3. ~~

   ~~'12'     // 12
   typeof ~~'12'       // number
  
   ~~'12s'    // 0
   typeof ~~'12s'      //number

Test

My platform: Mac OS X 10.8.4 Intel core i5 2.5GHz
Nodejs v0.10.15

1. convert '12' to 12

    function plusConvert(){
      console.time('plusConvert');
      for(var i = 0; i < 1000000; i++){
        +'12';
      }  
      console.timeEnd('plusConvert');
    }
    
    function multipConvert(){
      console.time('multipConvert');
      for(var i = 0; i < 1000000; i++){
        '12' * 1;
      }
      console.timeEnd('multipConvert');
    }
    
    function andnConvert(){
      console.time('andnConvert');
      for(var i = 0; i < 1000000; i++){
        ~~'12';
      }
      console.timeEnd('andnConvert');
    }
    
    function convert(){
      plusConvert();
      multipConvert();
      andnConvert();
    }
    
    convert();

And result times: 1000000:

+	39ms	38ms	39ms	39ms	38ms	39ms	39ms	38ms	38ms	38ms
* 1	47ms	53ms	51ms	49ms	46ms	44ms	42ms	43ms	44ms	41ms
~~	39ms	41ms	40ms	39ms	41ms	40ms	48ms	45ms	43ms	42ms

And result `times: 10000000`:

+	382ms	394ms	385ms	388ms	388ms	386ms	380ms	378ms	392ms	385ms
* 1	374ms	374ms	374ms	374ms	375ms	373ms	373ms	373ms	373ms	389ms
~~	358ms	359ms	356ms	357ms	358ms	359ms	356ms	363ms	358ms	358ms

2. convert `'12s'` to `NaN` or `0` ```javascript function plusConvert(){ console.time('plusConvert'); for(var i = 0; i < 1000000; i++){ +'12s'; } console.timeEnd('plusConvert'); }

  function multipConvert(){
    console.time('multipConvert');
    for(var i = 0; i < 1000000; i++){
      '12s' * 1;
    }
    console.timeEnd('multipConvert');
  }
  
  function andnConvert(){
    console.time('andnConvert');
    for(var i = 0; i < 1000000; i++){
      ~~'12s';
    }
    console.timeEnd('andnConvert');
  }
  
  function convert(){
    plusConvert();
    multipConvert();
    andnConvert();
  }
  
  convert();

And result `times: 1000000`:   
<table>
   <tr><td> + </td><td>100ms</td><td>115ms</td><td>98ms</td><td>98ms</td><td>112ms</td><td>120ms</td><td>107ms</td><td>106ms</td><td>107ms</td><td>104ms</td></tr>
   <tr><td>* 1</td><td>103ms</td><td>93ms</td><td>94ms</td><td>93ms</td><td>99ms</td><td>101ms</td><td>97ms</td><td>95ms</td><td>100ms</td><td>96ms</td></tr>
   <tr><td>~~</td><td>84ms</td><td>83ms</td><td>85ms</td><td>83ms</td><td>85ms</td><td>84ms</td><td>84ms</td><td>86ms</td><td>92ms</td><td>90ms</td></tr>
<table>

And result `times: 10000000`: 
<table>
   <tr><td> + </td><td>936ms</td><td>930ms</td><td>939ms</td><td>936ms</td><td>932ms</td><td>939ms</td><td>936ms</td><td>933ms</td><td>936ms</td><td>949ms</td></tr>
   <tr><td>* 1</td><td>922ms</td><td>929ms</td><td>929ms</td><td>924ms</td><td>925ms</td><td>922ms</td><td>940ms</td><td>925ms</td><td>924ms</td><td>941ms</td></tr>
   <tr><td>~~</td><td>822ms</td><td>821ms</td><td>825ms</td><td>841ms</td><td>824ms</td><td>823ms</td><td>824ms</td><td>823ms</td><td>824ms</td><td>826ms</td></tr>
<table>