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javascript - check if string begins with something?

我在:你可以使用^=检查,看看看看看看看看看看看看看看看看看看看看看看看看看看有无。

我引用这个例子:

var foo = "something-something";
if(foo ^= "something") {
    alert("works!");
}
else{
    alert("doesn t work :(");
}

但它没有工作——谁能这样做?

jsfiddle example here:

Answer 1

   var foo = "something-something";
if(foo.indexOf("something") === 0) {
    alert("works!");
}
else{
    alert("doesn t work :(");
}

See updated jsfiddle http://jsfiddle.net/M6dEM/3/

Answer 2

我认为,或许你正在考虑:

var x = "hello world!"
if (x.match(/^hello/)) {
   alert("I start with it!")
}

这使用了一种固定的表述(^):它必须找到对应投入的“hello”。

On the other hand, x ^= "foo" is the same as x = x ^ "foo", or a bit-wise exclusive or. In this case that is equivalent to x = "something-something" ^ "something" -> x = 0 ^ 0 -> 0 (which is a falsey value, and never true).

幸福 co。

Answer 3

替代方法:

if(foo.substring(0,"something".length) == "something") {
    alert("works!");
}
else{
    alert("doesn t work :(");
}

I edited my answer and replaced "9" with "something".length so now there s no hardcode anymore.

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