What’s the meaning of “=>” in TypeScript? (Fat Arrow)

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Perhaps you are confusing type information with a function declaration. If you compile the following:

var MakePoint: () => {x: number; y: number;};

you will see that it produces:

var MakePoint;

In TypeScript, everything that comes after the : but before an = (assignment) is the type information. So your example is saying that the type of MakePoint is a function that takes 0 arguments and returns an object with two properties, x and y, both numbers. It is not assigning a function to that variable. In contrast, compiling:

var MakePoint = () => 1;

produces:

var MakePoint = function () { return 1; };

Note that in this case, the => fat arrow comes after the assignment operator.

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