什么相当于PHP的“。=”在Javascript中，为变量添加一些东西..？

Question

In PHP you can do:

$myvar = "Hello";
$myvar .= " world!";
echo $myvar;

The output is: Hello world!

How can I do this in Javascript/jQuery..?

Answer 1

var a = 'Hello';
    a += ' world';
alert(a);

You'll get a dialog with "Hello world".

Be careful with this, though:

var a = 3;
    a += 'foo';

Result: 3foo . But:

var a = 3;
    a += 4;
    a += 'b';

You'll get an interesting result, and probably not the one you expect.

Answer 2

The PHP concatenation operator is .

The Javascript concatenation operator is +

So you're looking for +=

Answer 3

In JavaScript the string concatenation operation is + and the compound string concatenation and assignment operator is += . Thus:

var myvar = "Hello";
myvar += " world!";

Answer 4

Got it.

I was doing this:

var myvar = "Hello";
var myvar += " world!";
var myvar += " again!";

I guess the multiple var was my problem...

Thanks all.

Answer 5

+ is the String concatenation operator in Javascript. PHP and Javascript, both being loosely-typed languages, deal with conflicts between addition and concatentation in different ways. PHP deals with it by having a completely separate operator (as you stated, . ). Javascript deals with it by having certain rules for which operation is being performed. For that reason, you need to be aware of whether your variable is typed as a String or a Number.

Example:

• "1" + "3" : In PHP, this equals the number 4. In JavaScript, this equals "13". To get the desired 4 in Javascript, you would do Number("1") + Number("3") .

The basic idea in Javascript is that any two variables that are both typed as Numbers with a + operator in between will be added. If either is a string, they will be concatenated.

Answer 6

var a="Hello"; a+="world !";

output: Hello world!