JS: What's the difference between =+ and +=

Question

given the following block of code

var sumX = 0,
    sumY = 0,
    x = 1,
    y = 2;
sumX =+ x;
sumY += y;

What is the difference between the two assignment operators?

Please use the search: [`[javascript] "=+"`](http://stackoverflow.com/search?q=%5Bjavascript%5D+%22%3D%2B%22) — Felix Kling, Jan 12 '15 at 20:25

score 1 · Answer 1 · edited May 23 '17 at 12:05

1

sumY += y; adds y to sumY.
sumY =+ y; is equivalent to sumY = (+y);. For numbers, the unary plus operator is a no-op, so the entire expression simply assigns y to sumY.

edited May 23 '17 at 12:05

Community

answered Jan 12 '15 at 20:24

NPE

score 1 · Accepted Answer · answered Jan 12 '15 at 20:25

1

=+ will cast implicitly x to a number and assign sumX the value

+= will add x to sumX without an attempt at casting

answered Jan 12 '15 at 20:25

Travis J

2 Answers2