preface
This article briefly summarizes the commonly used depth comparison methods, which are widely used in React, especially prop comparison in the life cycle. React and immutable are inherently mutable. Assuming you don’t use immutable as a third party library in your project, this is a summary of how to implement deep comparison.
Methods a
[JavaScript]
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functionequalsObject (obj1,obj) {
varp;
if(obj1 === obj) {
returntrue;
}
// some checks for native types first
// function and sring
if(typeof(obj1) === "function"|| typeof(obj1) === "string"|| obj1 instanceofString) {
returnobj1.toString() === obj.toString();
}
// number
if(obj1 instanceofNumber || typeof(obj1) === "number") {
if(obj instanceofNumber || typeof(obj) === "number") {
returnobj1.valueOf() === obj.valueOf();
}
returnfalse;
}
// equalsObject(null,null) and equalsObject(undefined,undefined) do not inherit from the
// Object.prototype so we can return false when they are passed as obj
if(typeof(obj1) ! = =typeof(obj) || obj === null|| typeof(obj) === "undefined") {
returnfalse;
}
functionsort (o) {
varresult = {};
if(typeofo ! = ="object") {
returno;
}
Object.keys(o).sort().forEach(function(key) {
result[key] = sort(o[key]);
});
returnresult;
}
if(typeof(obj1) === "object") {
if(Array.isArray(obj1)) { // check on arrays
returnJSON.stringify(obj1) === JSON.stringify(obj);
} else{ // anyway objects
for(p inobj1) {
if(typeof(obj1[p]) ! = =typeof(obj[p])) {
returnfalse;
}
if((obj1[p] === null) !== (obj[p] === null)) {
returnfalse;
}
switch(typeof(obj1[p])) {
case'undefined':
if(typeof(obj[p]) ! = ='undefined') {
returnfalse;
}
break;
case'object':
if(obj1[p] ! = =null
&& obj[p] ! = =null
&& (obj1[p].constructor.toString() ! == obj[p].constructor.toString()
| |! equalsObject(obj1[p],obj[p]))) {
returnfalse;
}
break;
case'function':
if(obj1[p].toString() ! == obj[p].toString()) {
returnfalse;
}
break;
default:
if(obj1[p] ! == obj[p]) {
returnfalse;
}
}
};
}
}
// at least check them with JSON
returnJSON.stringify(sort(obj1)) === JSON.stringify(sort(obj));
}
vara = {a: 'text'B: [0, 1]};
varb = {a: 'text'B: [0, 1]};
varc = {a: 'text', b: 0};
vard = {a: 'text', b: false};
vare = {a: 'text'B: [1, 0]};
varf = {a: 'text'B: [1, 0], f:function() {this.f = this.b; }};
varg = {a: 'text'B: [1, 0], f:function() {this.f = this.b; }};
varh = {a: 'text'B: [1, 0], f:function() {this.a = this.b; }};
vari = {
a: 'text'.
c: {
b: [1, 0],
f: function() {
this.a = this.b;
}
}
};
varj = {
a: 'text'.
c: {
b: [1, 0],
f: function() {
this.a = this.b;
}
}
};
vark = {a: 'text', b: null};
varl = {a: 'text', b: undefined};
equalsObject(a,b) //true
equalsObject(f,g)//true
equalsObject(f,h)//false
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Method 2
[JavaScript]
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functiondeepCompare(x, y) {
vari, l, leftChain, rightChain;
functioncompare2Objects(x, y) {
varp;
// remember that NaN === NaN returns false
// and isNaN(undefined) returns true
if(isNaN(x) && isNaN(y) && typeofx === 'number'&& typeofy === 'number') {
returntrue;
}
// Compare primitives and functions.
// Check if both arguments link to the same object.
// Especially useful on the step where we compare prototypes
if(x === y) {
returntrue;
}
// Works in case when functions are created in constructor.
// Comparing dates is a common scenario. Another built-ins?
// We can even handle functions passed across iframes
if((typeofx === 'function'&& typeofy === 'function') | |
(x instanceofDate && y instanceofDate) ||
(x instanceofRegExp && y instanceofRegExp) ||
(x instanceofString && y instanceofString) ||
(x instanceofNumber && y instanceofNumber)) {
returnx.toString() === y.toString();
}
// At last checking prototypes as good as we can
if(! (xinstanceofObject && y instanceofObject)) {
returnfalse;
}
if(x.isPrototypeOf(y) || y.isPrototypeOf(x)) {
returnfalse;
}
if(x.constructor ! == y.constructor) {
returnfalse;
}
if(x.prototype ! == y.prototype) {
returnfalse;
}
// Check for infinitive linking loops
if(leftChain.indexOf(x) > -1 || rightChain.indexOf(y) > -1) {
returnfalse;
}
// Quick checking of one object being a subset of another.
// todo: cache the structure of arguments[0] for performance
for(p iny) {
if(y.hasOwnProperty(p) ! == x.hasOwnProperty(p)) {
returnfalse;
} elseif(typeofy[p] ! = =typeofx[p]) {
returnfalse;
}
}
for(p inx) {
if(y.hasOwnProperty(p) ! == x.hasOwnProperty(p)) {
returnfalse;
} elseif(typeofy[p] ! = =typeofx[p]) {
returnfalse;
}
switch(typeof(x[p])) {
case'object':
case'function':
leftChain.push(x);
rightChain.push(y);
if(! compare2Objects(x[p], y[p])) {
returnfalse;
}
leftChain.pop();
rightChain.pop();
break;
default:
if(x[p] ! == y[p]) {
returnfalse;
}
break;
}
}
returntrue;
}
if(arguments.length < 1) {
returntrue; //Die silently? Don't know how to handle such case, please help...
// throw "Need two or more arguments to compare";
}
for(i = 1, l = arguments.length; i < l; i++) {
leftChain = []; //Todo: this can be cached
rightChain = [];
if(! compare2Objects(arguments[0], arguments[i])) {
returnfalse;
}
}
returntrue;
}
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Methods three
[JavaScript]
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functioncountProps(obj) {
varcount = 0;
for(k inobj) {
if(obj.hasOwnProperty(k)) {
count++;
}
}
returncount;
};
functionobjectEquals(v1, v2) {
if(typeof(v1) ! = =typeof(v2)) {
returnfalse;
}
if(typeof(v1) === "function") {
returnv1.toString() === v2.toString();
}
if(v1 instanceofObject && v2 instanceofObject) {
if(countProps(v1) ! == countProps(v2)) {
returnfalse;
}
varr = true;
for(k inv1) {
r = objectEquals(v1[k], v2[k]);
if(! r) {
returnfalse;
}
}
returntrue;
} else{
returnv1 === v2;
}
}
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Methods four
[JavaScript]
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const hasOwnProperty = (obj1: any, obj2: any) => {
switch(typeOf(obj1)) {
case"object":
returnObject.prototype.hasOwnProperty.call(obj1, obj2);
case"array":
returntypeOf(obj2) === "number"&& obj2 >= 0 && obj1.length > obj2 ;
default:
returnfalse;
}
};
const typeOf = (value) => Object.prototype.toString.call(value).replace(/\[|\]/gi, "").split("")[1].toLowerCase();
const length = (object) => {
switch(typeOf(object)) {
case"array":
returnobject.length;
case"object":
returnObject.keys(object).length;
default:
return0;
}
};
const every = (obj, func) => typeOf(obj) === "array"? obj.every(func) : Object.entries(obj).every(([key, value]: [any, any]) => func(value, key));
const equal = (obj1, obj2) => {
switch(true) {
casetypeOf(obj1) === "function"&& typeOf(obj2) === "function":
returntrue;
caseobj1 === obj2:
returntrue;
casetypeOf(obj1) === typeOf(obj2) && ["object"."array"].includes(typeOf(obj1)) && length(obj1) === length(obj2):
returnevery(obj1, (value, key) => hasOwnProperty(obj2, key) && equal(value, obj2[key]));
default:
returnfalse;
}
};
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This article from: https://www.haorooms.com/post/js_deepcompare