Javascript Best Practices - The Diigo Meta page

• 27 Aug 09
  

  Eduardo Bernal

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  Lourens Keyser

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• 10 Apr 09
  

  Javier Neira

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• 09 Apr 09
  

  R. H.

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• 17 Jan 09
  

  Lite

  Introduction
  
  This document is a list of best practices and preferred ways of developing javascript code, based on opinions and experience from many developers in the javascript community. Since this is a list of recommendations rather than a list of absolute rules, experienced developers may have slightly differing opinions from those expressed below.
  
  Table Of Contents
  
  1. Always Use 'var'
  2. Feature-Detect Rather Than Browser-Detect
  3. Use Square Bracket Notation
  4. Avoid 'eval'
  5. Reference Forms and Form Elements Correctly
  6. Avoid 'with' Statements
  7. Use onclick In Anchors Instead Of javascript: Pseudo-Protocol
  8. Use The Unary + Operator To TypeConvert To Number
  9. Avoid document.all
  10. Don't Use HTML Comments In Script Blocks
  11. Avoid Cluttering The Global Namespace
  12. Avoid sync "Ajax" calls
  13. Use JSON
  14. Use Correct <script> Tags
  
  Always Use 'var'
  
  Variables in javascript either have global scope or function scope, and using the 'var' keyword is vital to keeping them straight. When declaring a variable for use either as a global variable or as a function-level variable, always prefix the declaration with the 'var' keyword. The example below highlights the potential problem caused by not doing so.
  Problem Caused By Not Using Var
  
  var i=0; // This is good - creates a global variable
  function test() {
  for (i=0; i<10; i++) {
  alert("Hello World!");
  }
  }
  test();
  alert(i); // The global variable i is now 10!
  
  Since the variable i inside the function was not declared as a function-level variable by using the 'var' keyword, it references the global variable in this example. It is a good idea to always declare global variables using 'var', but it is vital to declare function-scoped variables using 'var'. The two approaches below are functionally identical.
  Fixed Function
  
  function test() {
  var i=0;
  for (i=0; i<10; i++) {
  alert("Hello World!");
  }
  }
  
  Fixed Function
  
  function test() {
  for (var i=0; i<10; i++) {
  alert("Hello World!");
  }

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• 13 Jan 09
  

  Navneet Kumar

  JavaScript best_practices BestPractices tipsntricks

  • if it returns true, then the HREF of the anchor will be followed like a normal link. If it returns false, then the HREF will be ignored. This is why "return false;"
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• 06 May 07
  

  Gavin Allan

  This document is a list of best practices and preferred ways of developing javascript code, based on opinions and experience from many developers in the javascript community.

  javascript reference

• 27 Dec 06
  

  Adam Skinner

  javascript mattkruse tips

  • 
    With dot notation, the property name is hard-coded and cannot be changed at run-time. With bracket notation, the property name is a string which is evaluated to resolve the property name. The string can be hard-coded, or a variable, or even a function call which returns a string property name.
  • Prefixing a variable or expression with + will force it to evaluate as a number, which can then be successfully used in a math operation.
  • 1 more annotations...
  • • The javascript code that runs within the onclick handler must return true or false (or an expression than evalues to true or false) back to the tag itself - if it returns true, then the HREF of the anchor will be followed like a normal link. If it returns false, then the HREF will be ignored. This is why "return false;" is often included at the end of the code within an onclick handler.
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  ippy04

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