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Home php教程 PHP源碼 在javascript中使用php風(fēng)格的$globals

在javascript中使用php風(fēng)格的$globals

Jun 08, 2016 pm 05:32 PM
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在javascript中使用php風(fēng)格的$globals

JavaScript有隱含的全局變量。當(dāng)你不使用var來定義a = 1,而直接定義a=1時(shí),這個(gè)變量a將成為一個(gè)全局變量。有的認(rèn)為這是一個(gè)錯(cuò)誤,應(yīng)該避免全局變量,因?yàn)樗鼈兺鶗?huì)在意想不到的地方出錯(cuò),尤其是在項(xiàng)目參與人員很多的情況下。

在PHP當(dāng)中,默認(rèn)的是局部變量。如果你需要一個(gè)全局變量,那么你必須要將要聲明為全局變量的變量放到$globals這個(gè)數(shù)組中。

怎樣在javascripts中使用$globals呢?通過為全局公約在你的javascripts呢?在腳本文件頂部聲明:
$GLOBALS = {};
那么每一次當(dāng)你需要一個(gè)全局變量,您可以這樣做:

$GLOBALS[ '' myglob '' ] = 1 ; / /非常像PHP的樣式

或者如果你喜歡,也可以這樣:

$globals.myglob = 1 ;
這樣做的優(yōu)點(diǎn):

???? *全局變量容易識(shí)別(甚至從飛機(jī)都可以看見)
???? *如果變量不定義成$GLOBAL,那么它就是局部變量。如果變量沒有使用var,那么它將產(chǎn)生一個(gè)錯(cuò)誤

缺點(diǎn):

???? *這種使用方法,不是官方規(guī)定的,不強(qiáng)制使用,只是一項(xiàng)約定俗成的方法。

?

?

Stoyan Stefanov''s Blog: PHP-style $GLOBALS in Javascript?

Javascript has implied globals. When you skip the var in var a = 1; and go a = 1;, then a becomes a global variable. Some consider this an error in the language. Global variables should be avoided because they tend to overwrite each other in unexpected places, especially if the project grows in LOC and number of developers.
In PHP on the other hand, variables are local. If you need a global variable, then you have to have to be explicit about it using the $GLOBALS superglobal array.
So how about this: adopt the $GLOBALS convention in your JavaScripts? At the top of the script you go:
$GLOBALS = {};
Then every time you need a global variable, you do:
$GLOBALS[''myglob''] = 1; // very PHP-like
or if you prefer:
$GLOBALS.myglob = 1;
Benefits of the approach:
??global variables easy to spot (even from an aeroplane)
??if it''s not $GLOBAL, it''s meant to be local. If it''s missing the var, it''s an error
Drawback:
??It''s a convention, so it can only help, but not enforce any coding practices

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