它在Javascript中的意义(分配变量)
这个问题在这里已经有了答案:
||
有效地像SQL COALESCE
语句一样工作。
var x = y || z;
手段:
如果y
计算结果为“truthy”的值,分配y
到x
。
如果y
评估为“falsy”值,则将z
分配给x
。
请参阅http://11heavens.com/falsy-and-truthy-in-javascript了解更多关于“truthy / falsy”(或者仅仅是google)的细节。
||
是一个or
运营商。
它基本上意味着如果variable
未定义,它会将variable
分配给新的对象文字。
https://developer.mozilla.org/en-US/docs/JavaScript/Guide/Expressions_and_Operators#Logical_operators
||
这意味着或这里:
var x = 5
var x = x || {} //If v is defined, v = v, else v = {} (new, empty, object).
//x = 5 since x already was defined
var y = y || {}
//y = {} since y was undefined, the second part is run.
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