JavaScript Patterns 2.3 - For loops

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HTMLCollections are objects returned by DOM methods such as:

? document.getElementsByName()

? document.getElementsByClassName()

? document.getElementsByTagName()

HTMLCollections, which were introduced before the DOM standard and are still in use today

document.images

All IMG elements on the page

document.links

All A elements

document.forms

All forms

document.forms[0].elements

All fields in the first form on the page

// used i+=1 instead of i++ to follow the rule of JSLint

for (var i = 0, max = myarray.length; i < max; i += 1) {

    // do something with myarray[i]

}  

? Use one less variable (no max)

? Count down to 0, which is usually faster because it‘s more efficient to compare to 0 than to the length of the array or to anything other than 0

The first modified pattern is:

var i, myarray = [];

for (i = myarray.length; i--;) {

    // do something with myarray[i]

} 

And the second uses a whileloop:

var myarray = [],
i = myarray.length;

while (i--) {

    // do something with myarray[i]

} 

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JavaScript Patterns 2.3 - For loops

标签：style   blog   class   code   c   java   

原文地址：http://www.cnblogs.com/haokaibo/p/for-loops.html