Why are () omitted when adding function as an object property like in this code?

Question

This is a section of code from https://bl.ocks.org/mbostock/3014589

Why are () omitted after the functions assigned to "interpolate"? How is it different from with ()?

Thank you

var spaces = [
  {name: "HSL", interpolate: d3.interpolateHsl},
  {name: "HCL", interpolate: d3.interpolateHcl},
  {name: "Lab", interpolate: d3.interpolateLab},
  {name: "RGB", interpolate: d3.interpolateRgb}
];

Are you trying to assign the function? Or the output of calling the function? — 4castle, Mar 07 '17 at 04:23
Do you mean like this: `{interpolate: (d3.interpolateHsl)}` ? — slebetman, Mar 07 '17 at 04:26

score 3 · Answer 1 · edited May 23 '17 at 12:17

3

Without the parentheses, you're referencing the function itself. If you put the ()'s, you're actually calling the function and returning the result (if any). So by putting the name of the function in there, whatever uses the object and references the interpolate attribute can evaluate that function. For example, see this post.

edited May 23 '17 at 12:17

Community

1
1

answered Mar 07 '17 at 04:26

Will Jobs

362
1
11

Why are () omitted when adding function as an object property like in this code?

1 Answers1