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polyfill an ES5-ish Array.prototype.map
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| // based loosely on Kris Kowal's es-5shim.js | |
| // https://github.com/kriskowal/es5-shim/blob/master/es5-shim.js#L204 | |
| // | |
| // due to space constraints, this version does not check function type or cast length to a number | |
| [].map || ( // if arrays have no map | |
| Array.prototype.map = // set the prototype's map | |
| function( // to a function | |
| a // that takes a mapping function | |
| /*, thisp */ // and an optional scope. | |
| ){ | |
| for ( | |
| var b = this // cache `this` and | |
| , c = b.length // the array's length, | |
| , d = [] // create the return array | |
| , e = 0 // and initialize the cursor, | |
| , f // and cache undefined. | |
| ; e < b; // while the cursor is less than the length | |
| ) d[e] = // set the result member | |
| e in b // if it originally exists, | |
| ? a.call( // to the given function, called with | |
| arguments[1], // the optional scope, | |
| b[e], // existing member, | |
| e++, // member index, and | |
| b ) // current scope, | |
| : f; // or to undefined otherwise. | |
| return d // return the result. | |
| }) |
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| [].map||(Array.prototype.map=function(a){for(var b=this,c=b.length,d=[],e=0,f;e<b;)d[e]=e in b?a.call(arguments[1],b[e],e++,b):f;return d}) |
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| DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE | |
| Version 2, December 2004 | |
| Copyright (C) 2011 Jed Schmidt <http://jed.is> | |
| Everyone is permitted to copy and distribute verbatim or modified | |
| copies of this license document, and changing it is allowed as long | |
| as the name is changed. | |
| DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE | |
| TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION | |
| 0. You just DO WHAT THE FUCK YOU WANT TO. |
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| { | |
| "name": "map", | |
| "description": "polyfill an ES5-compatibile Array.prototype.map where needed.", | |
| "keywords": [ | |
| "array", | |
| "map", | |
| "es5", | |
| "polyfill" | |
| ] | |
| } |
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| <!DOCTYPE html> | |
| <title>Foo</title> | |
| <div>Expected value: <b>2,4,6,8</b></div> | |
| <div>Actual value: <b id="ret"></b></div> | |
| <script> | |
| var map = | |
| [].map||(Array.prototype.map=function(a){for(var b=this,c=b.length,d=[],e=0,f;e<b;)d[e]=e in b?a.call(arguments[1],b[e],e++,b):f;return d}) | |
| document.getElementById( "ret" ).innerHTML = map.call([1,2,3,4], function(x){ return x*2 }) | |
| </script> |
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@atk Found a typo in your version (you misspelled
lengthaslengh). So just in case anyone wishes to use your version of the snippet, here it is fixed:[].map||(Array.prototype.map=function(a,t){for(var c=this,b=c.length,d=[],e=0;e<b;)e in c&&(d[e]=a.call(t,c[e],e++,c));d.length=b;return d})