Is there a quicker way to write conditional statements?

I have a statement like this:

 if(window.location.hash != '' && window.location.hash != '#all' &&开发者_运维百科amp; window.location.hash != '#')

Can I write it so I only have to mention window.location.hash once?

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the obvious way to do this is:

var h = window.location.hash;
if (h != '' && h != '#all' && h != '#')

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you can use the in operator and an object literal:

if (!(window.location.hash in {'':0, '#all':0, '#':0}))

this works by testing the keys of the object (the 0's are just filler).

Also note that this may break if you are messing with object's prototype

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Regular expression? Not so readable, but concise enough:

if (/^(|#|#all)$/.test(window.location.hash)) {
    // ...
}

This also works:

if (window.location.hash.match(/^(|#|#all)$/)) {
    // ...
}

... but it's less efficient, per Ken's comment.

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Use indexOf for newer browsers, and supply an implementation for older browsers which you can find here.

// return value of -1 indicates hash wasn't found
["", "#all", "#"].indexOf(window.location.hash)

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Just an addition, because besides quite good variety of do not repeat yourself approaches, nobody mentioned that:

In browsers, window is Global object, so cut it off, if you dont have another property named "location" in the current scope (unlikely). location.hash is enough

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I think it is good to check on length since the first character always is an hash.

var h = location.hash;
if ( h.length > 1 && h != '#top' )