X + = y + = z in Javascript

Question

I know in javascript

x = y = z means x = z and y = z

x+=z means x=x+z ;

So, if I want x=x+z and y=y+z , I tried x+=y+=z not work

does anyone have an idea to write a short code instead of x+=z;y+=z

EDIT

First thanks to everyone who is involved in my question. Here I want to explain why I have this question in the first place.

I tried to write code like x+='some html code' and I need y+='the same html code' . Therefore, naturally, I do not want to first create another var z='the html code , and then x+=z and y+=z

Hope my clarify the meaning. Anyway, I'm going to close this question now. Thanks again.

Answer 1

Assuming padding and not concatenation , this works:

 x -= y - (y += z); 

but seriously, don't use it !

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For those who want to find out how the evaluation sequence (where I use n to display the current intermediate result) is approximately equal to:

 n = y1 = y0 + z // n = y = (y + z) n = y0 - y1 // -> n == -z [uses the original value of y] x -= n // -> x += z 

Answer 2

Just use this:

 x+=z;y+=z 

Honestly, everything else will just force someone else to support your code so that it stops and scratches its head for a couple of minutes. This code is not shocking for a long time ...

Answer 3

Well, x + = y + = z means:

• x = x + y + z
• y = y + z

Thus, it is impossible to do x = x + z and y = y + z with x + = y + = z, because this means:

 x += (y = y + z) -> x = x + (y = y + z) 

Take the following example:

 function sum () { var x = 5, y = 7, z = 3; x += y += z; console.log (x); // it shows 15 --> x = 5 + 7 + 3 console.log (y); // it shows 10 --> y = 7 + 3 console.log (z); // it shows 3 } 

So you should do it like this:

 x += z; y += z; 

Answer 4

In fact, x = y = z does not mean x = z and y = z . This means calculating the value of the expression y = z , and then assign x the value of this expression. You are wrong here.

Answer 5

you can also do .. x = 1, y = 2, z = 3

 x+=(y+=z)-(yz) 

Answer 6

You can use the comma operator:

 x += (y+=z,z); 

Answer 7

It does not work, because what is done in the assignment

 x += y += z; 

is an:

 y += z 

ranked first. Besides adding z to x , this assignment also returns a new y value as the return value. Then this new y value becomes the operand for the other += .

 x += y 

Well, there is probably no shorter way to write what you want than just

 x += z; y += z; 

Answer 8

FWIW, in Firefox, you can use the destructuring assignment to do something like what you want.

 Array.prototype.addToEach = function(x) { for (var i = 0; i < this.length; i++) this[i] += x; return this; }; var x = "foo", y = "bar"; [x,y] = [x,y].addToEach("baz"); console.log(x,y); // "foobaz" "barbaz" 

http://jsfiddle.net/uPzNx/ (demo for spidermonkey implementation)

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Not that this has anything to do with the solution, but for those who don't like the native .prototype extensions, you can do it instead.

 function addToEach(s) { var args = Array.prototype.slice.call(arguments, 1); for (var i = 0; i < args.length; i++) args[i] += s; return args; }; var x = "foo", y = "bar"; [x,y] = addToEach("baz", x, y); console.log(x,y); // "foobaz" "barbaz" 

Answer 9

This works on jsfiddle, so it should be something else that you do ...

 x = 1, y = 2, z = 3; x += y += z; alert(x);