JavaScript APIs In Focus

JavaScript APIs In Focus

• 1.
  JavaScript APIs inFocus (with a short rant on quality of APIs in public libraries and a direction to what and why should be made better) Amsterdam JS meeting 7th September 2010 Sergey Ilinsky ( @ilinsky )
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  1. What iswrong with my code? (bad library story) jQuery: > $(document).each() TypeError: b is undefined > $(document).click("alert(1)") TypeError: d is undefined > $(document).map(null) TypeError: a is null Dojo: > dojo.stopEvent() TypeError: evt is undefined > dojo.ready([new Function]) TypeError: mll[x] is not a function > dojo.map(null) TypeError: arr is null
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  1. What iswrong with my code? (good library story) An other library (Ample SDK): > ample.documentElement.removeChild() Missing required 1st argument "node" in "removeChild" function call > ample.querySelector("xul|textbox[type=number]", 11); Incompatible type of 2nd argument "NSResolver" in "querySelector" function call. Expecting "Function" > ample.importNode(null) null is not allowed value of 1st argument "node" in "importNode" function call
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  2. Why isit important to validate library API call?
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  2. Why isit important to validate library API call? 1) Helps library user (end developer) to find problems more efficiently
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  2. Why isit important to validate library API call? 1) Helps library user (end developer) to find problems more efficiently 2) Prevents library from internal failure caused by improper call
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  3. Three aspectsof API call validation 1) Arguments requiredness 2) Arguments' Datatypes
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  3) null values
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  4. Guard.js —API validation library Guard.js is a “broker library” that helps you validating API calls to your “public library». 4.1) Using Guard.js 4.2) Guard exceptions in try/catch statements 4.3) Data types support 4.4) Validation execution overhead
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  4.1 Using Guard.js// Your «public library» code myObject.myFunction = function(sName, fHandler, bDirection, oArguments) { // Validate API function call Guard(arguments, [ // 'name' is required, must be string ["name", String], // 'handler' is required, must be function ["handler", Function], // 'direction' is optional, if passed must be boolean or null ["direction", Boolean, true, true], // 'arguments' is optional, if passed must be JS arguments object ["arguments", Guard.Arguments, true] ]); // Execute your library function here return "the output of myLibraryFunction"; };
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  4.2 Guard exceptionsin try/catch statements function testMyObjectFunction() { try { myObjectFunction(3); } catch (e) { alert(e.caller) // -> testMyObjectFunction } } testMyObjectFunction();
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  4.3 Data typessupport - Primitive Types - String - Number - Boolean - Object - «Object» Types - Array - Function - Date - RegExp - Special Types - Guard.Arguments - Custom Types - Any constructor function reference
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  10% 4.4 Validationexecution overhead
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  5. Signing JavaScriptObjects if (!window.XMLHttpRequest) { window.XMLHttpRequest = function() { return new ActiveXObject(“Microsoft.XMLHTTP”); } } 1) Signing Object window.XMLHttpRequest.prototype.toString = function() { return “[object XMLHttpRequest]”; } alert(new XMLHttpRequest) // [object XMLHttpRequest] 2) Signing Function window.XMLHttpRequest.toString = function() { return “function XMLHttpRequest() {\n\t[my library code]\n}”; } alert(XMLHttpRequest) // function XMLHttpRequest() { [my library code] }
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  Guard.js Web-Site: http://github.com/ilinsky/guard.js Ample SDK Web-Site: http://www.amplesdk.com
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  Sergey Ilinsky
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  http://www.ilinsky.com
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  http://twitter.com/ilinsky 6. Links