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Return unsub function from on() #42

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Return unsub function from on() #42

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13 changes: 8 additions & 5 deletions src/index.js
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Original file line number Diff line number Diff line change
Expand Up @@ -14,9 +14,10 @@ type EventHandlerMap = {
* @returns {Mitt}
*/
export default function mitt(all: EventHandlerMap) {
all = all || Object.create(null);
all = all || {};
let instance;

return {
return instance = {
/**
* Register an event handler for the given type.
*
Expand All @@ -26,7 +27,9 @@ export default function mitt(all: EventHandlerMap) {
* @memberOf mitt
*/
on(type: string, handler: EventHandler) {
(all[type] || (all[type] = [])).push(handler);
var arr = all[type] = all[type] || [];
arr.push(handler);
return instance.off.bind(instance, type, handler);
},

/**
Expand All @@ -38,8 +41,8 @@ export default function mitt(all: EventHandlerMap) {
* @memberOf mitt
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@tunnckoCore tunnckoCore Feb 28, 2017

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I believe that's intentional.

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@developit developit Feb 28, 2017

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the assignment isn't needed, just it produced a smaller output size because it is duplicated and thus cheap when gzipped. I'd be curious to see the size with & without this change.

*/
off(type: string, handler: EventHandler) {
let e = all[type] || (all[type] = []);
e.splice(e.indexOf(handler) >>> 0, 1);
var arr = all[type] || [];
arr.splice(arr.indexOf(handler) >>> 0, 1);
},

/**
Expand Down
18 changes: 18 additions & 0 deletions test/index.js
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Original file line number Diff line number Diff line change
Expand Up @@ -58,6 +58,13 @@ describe('mitt#', () => {
expect(events).to.not.have.property('bar');
expect(events).to.have.property('baz:baT!').that.deep.equals([foo]);
});

it('should return unsubscribe function', () => {
let foo = () => {};
let off = inst.on('foo', foo);

expect(off).to.be.a('function');
});
});

describe('off()', () => {
Expand Down Expand Up @@ -91,6 +98,17 @@ describe('mitt#', () => {
expect(events).to.not.have.property('bar');
expect(events).to.have.property('baz:baT!').that.is.empty;
});

it('should remove handler if unsubscribe is called', () => {
let foo = () => {};
let off = inst.on('foo', foo);

expect(events).to.have.property('foo').that.deep.equals([foo]);

off();

expect(events).to.have.property('foo').that.is.empty;
});
});

describe('emit()', () => {
Expand Down