💾deepEqual()
JS ⟩ value ⟩ function ⟩ recursive ⟩ deepEqual()
returns true only if they are
the same value or
objects with properties of the same keys/values, where the values are compared with a recursive call to deepEqual.
replit ⟩ deepEqual(a, b)
function deepEqual(a, b) {
// check if `value` is (non-function) object
function isNonFunctionObject(value) {
return typeof value === 'object' && value !== null;
}
// 1. same value -> always equal
if (a === b) return true;
// 2. a !== b
// 2.1 (either one is primitive/function) different values -> always unequal
if(!isNonFunctionObject(a) || !isNonFunctionObject(b)) return false;
// 2.2 both (non-function, different) objects
// - count properties
const keysA = Object.keys(a), keysB = Object.keys(b);
if (keysA.length !== keysB.length) return false;
// - check property keys/values
for (const key of keysA) {
if (!keysB.includes(key) || !deepEqual(a[key], b[key])) return false;
}
// - property keys/values all match
return true;
}
💈範例:
// test
let obj = {
x: {y: "a"},
z: 2,
};
[
[x => x, x => x], // ⨉ (different functions)
[obj, obj], // ○ (same object)
[obj, {x: 1, z: 2}], // ⨉
[obj, {x: {y: "a"}, z: 2}], // ○
[1, 2], // ⨉
[1, 1], // ○
[obj, 1], // ⨉
[{x: undefined}, {}], // ⨉
].forEach(([a,b]) => {
console.log(deepEqual(a,b)) // ✅ test "deepEqual"
});
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