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Simpify getting object type name #7159

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merged 2 commits into from
Oct 15, 2018
Merged

Simpify getting object type name #7159

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3edd13e
Simpify getting object type name
Connormiha Oct 13, 2018
e3f4643
Add info to changelog
Connormiha Oct 15, 2018
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69 changes: 42 additions & 27 deletions packages/jest-mock/src/index.js
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Original file line number Diff line number Diff line change
Expand Up @@ -173,31 +173,36 @@ function matchArity(fn: any, length: number): any {
return mockConstructor;
}

function isA(typeName: string, value: any): boolean {
return Object.prototype.toString.apply(value) === '[object ' + typeName + ']';
function getObjectType(value: any): string {
return Object.prototype.toString.apply(value).slice(8, -1);
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Do you have any perf benchmarks showing that this slice is not slowing down the whole caching effort?

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slice(8, -1) works 4x faster than concatanation '[object ' + typeName + ']'.

Source of my test.

const map1 = new Map();
const map2 = new Map();
let start;

function isA(typeName, value) {
  return Object.prototype.toString.apply(value) === '[object ' + typeName + ']';
}

function getObjectType(value) {
  return Object.prototype.toString.apply(value).slice(8, -1);
}

console.log('isA');
console.log('=======================');

start = process.hrtime()[1];
const compare1 = isA('Map', map1);
console.log(process.hrtime()[1] - start, compare1);


console.log('');
console.log('getObjectType');
console.log('=======================');
start = process.hrtime()[1];
const compare2 = getObjectType(map1) === 'Map';
console.log(process.hrtime()[1] - start, compare2);

Result of my tests (nano seconds):

isA
=======================
208620 true

getObjectType
=======================
57268 true

Tested on Node v10.10.0, MacOs.

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This is single execution without a warmup, hard to tell if it's representative. Can your run it on jsperf? Something like here https://twitter.com/bmeurer/status/867277137564360704?s=21

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The gain in jest's case is probably from doing the toString once instead of up to 12 times.

I doubt slice or not makes much of a difference. I don't think this is super hot code anyways - it's only used when generating mocks

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Ok. full test.
Test compares original getType(with many isA calls) and getType from this PR with chaching.

https://jsperf.com/object-prototype-tostring-caching

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here's the result:

fwiw, performance aside, I think this code is easier to read and maintain so I'm +1

}

function getType(ref?: any): string | null {
const typeName = getObjectType(ref);
if (
isA('Function', ref) ||
isA('AsyncFunction', ref) ||
isA('GeneratorFunction', ref)
typeName === 'Function' ||
typeName === 'AsyncFunction' ||
typeName === 'GeneratorFunction'
) {
return 'function';
} else if (Array.isArray(ref)) {
return 'array';
} else if (isA('Object', ref)) {
} else if (typeName === 'Object') {
return 'object';
} else if (
isA('Number', ref) ||
isA('String', ref) ||
isA('Boolean', ref) ||
isA('Symbol', ref)
typeName === 'Number' ||
typeName === 'String' ||
typeName === 'Boolean' ||
typeName === 'Symbol'
) {
return 'constant';
} else if (isA('Map', ref) || isA('WeakMap', ref) || isA('Set', ref)) {
} else if (
typeName === 'Map' ||
typeName === 'WeakMap' ||
typeName === 'Set'
) {
return 'collection';
} else if (isA('RegExp', ref)) {
} else if (typeName === 'RegExp') {
return 'regexp';
} else if (ref === undefined) {
return 'undefined';
Expand All @@ -209,21 +214,31 @@ function getType(ref?: any): string | null {
}

function isReadonlyProp(object: any, prop: string): boolean {
return (
((prop === 'arguments' ||
prop === 'caller' ||
prop === 'callee' ||
prop === 'name' ||
prop === 'length') &&
(isA('Function', object) ||
isA('AsyncFunction', object) ||
isA('GeneratorFunction', object))) ||
((prop === 'source' ||
prop === 'global' ||
prop === 'ignoreCase' ||
prop === 'multiline') &&
isA('RegExp', object))
);
if (
prop === 'arguments' ||
prop === 'caller' ||
prop === 'callee' ||
prop === 'name' ||
prop === 'length'
) {
const typeName = getObjectType(object);
return (
typeName === 'Function' ||
typeName === 'AsyncFunction' ||
typeName === 'GeneratorFunction'
);
}

if (
prop === 'source' ||
prop === 'global' ||
prop === 'ignoreCase' ||
prop === 'multiline'
) {
return getObjectType(object) === 'RegExp';
}

return false;
}

class ModuleMockerClass {
Expand Down