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Compare two similar/identical javascript objects for differences. Returns the changed properties filled with updated value, and unchanged fields with null.
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export class ObjectDiff { | |
isObject(obj: Object): boolean { | |
return typeof obj === 'object' && !Array.isArray(obj) | |
} | |
isArray(obj: Object): boolean { | |
return Array.isArray(obj) | |
} | |
isPrimitive(obj: Object): boolean { | |
return typeof obj !== 'object' | |
} | |
/** | |
* Checks a property of an object value of which is of primitive type (string, number, boolean) | |
* for changes and returns the changed value, otherwise null | |
*/ | |
diffPrimitive(path: string, beforeObj: Object, afterObj: Object): any | null { | |
if (!beforeObj || !afterObj) return null | |
if (beforeObj[path] !== afterObj[path]) | |
return afterObj[path] | |
return null | |
} | |
/** | |
* Checks two objects for differences and returns the changed properties filled | |
* with updated value, and unchanged fields with null | |
*/ | |
diffObject(beforeObj: Object, afterObj: Object): any { | |
if (!beforeObj || !afterObj) return | |
const result = {} | |
Object.keys(beforeObj).forEach(key => { | |
if (this.isPrimitive(beforeObj[key])) | |
result[key] = this.diffPrimitive(key, beforeObj, afterObj) | |
if (this.isObject(beforeObj[key])) | |
result[key] = this.diffObject(beforeObj[key], afterObj[key]) | |
if (this.isArray(beforeObj[key])) | |
result[key] = this.diffArray(beforeObj[key], afterObj[key]) | |
}) | |
return result | |
} | |
/** | |
* Checks two arrays for differences and returns the changed elements filled | |
* with updated value, and unchanged elements with null. The elements can be | |
* object or array as well. | |
*/ | |
diffArray(beforeArray: Array<any>, afterArray: Array<any>): Array<any> { | |
if (!beforeArray || !afterArray) return | |
const result = [ ...beforeArray ] | |
for(let i = 0; i < beforeArray.length; i++) { | |
if (this.isPrimitive(beforeArray[i])) | |
beforeArray[i] === afterArray[i] | |
? result[i] = null | |
: result[i] = afterArray[i] | |
if (this.isObject(beforeArray[i])) | |
result[i] = this.diffObject(beforeArray[i], afterArray[i]) | |
if (this.isArray(beforeArray[i])) | |
result[i] = this.diffArray(beforeArray[i], afterArray[i]) | |
} | |
return result | |
} | |
} | |
/******************* | |
* Tests * | |
*******************/ | |
let main = new ObjectDiff() | |
const a = { | |
test: "test", | |
same: "same", | |
nested: { | |
x: "x" | |
}, | |
arr: [ 1, 2, 7], | |
arrObjs: [ | |
{ y: "y"}, | |
{ z: "z"} | |
] | |
} | |
const b = { | |
test: "test1", | |
same: "same", | |
nested: { | |
x: "x" | |
}, | |
arr: [ 1, 2, 3], | |
arrObjs: [ | |
{ y: "y"}, | |
{ z: "a"} | |
] | |
} | |
const res = main.diffObject(a, b) | |
console.log(res) | |
/** | |
* Should print: | |
* { | |
* test: 'test1', | |
* same: null, | |
* nested: { x: null }, | |
* arr: [ null, null, 3 ], | |
* arrObjs: [ { y: null }, { z: 'a' } ] | |
* } | |
* | |
* | |
* Run file | |
* | |
* `tsc objectdiff.ts && node objectdiff.js` | |
*/ |
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Would you replace
console.log
with Assert methods? For example, using Mocha.js and Chai.jshttps://journal.artfuldev.com/unit-testing-node-applications-with-typescript-using-mocha-and-chai-384ef05f32b2