js实现深度比较

function isEqual(x, y) {
    // 如果全等则直接返回 true
    if (x === y) {
        return true;
    } else if (
        typeof x === "object" &&
        x !== null &&
        typeof y === "object" &&
        y !== null
    ) {
        let xKeys = Object.keys(x);
        let yKeys = Object.keys(y);
        // 如果key的数量不一致，直接返回 false;
        if (xKeys.length !== yKeys.length) {
            return false;
        }
        for (const key of xKeys) {
            if (x[key] === y[key]) {
                return true;
            } else {
                return false;
            }
        }
    } else {
        return false;
    }
}
console.log(isEqual([1, 2, 3], [1, 2, 3])); // true
console.log(isEqual([1, 2, 3], [1, 2, 3, 5])); // false
console.log(isEqual(null, undefined)); // false
console.log(isEqual(null, true)); // false
console.log(isEqual(null, false)); // false
console.log(isEqual(undefined, 0)); // false
console.log(isEqual(null, null)); // true
console.log(isEqual(NaN, NaN)); // false
console.log(isEqual(false, 0)); // false
console.log(isEqual({ a: 1 }, { a: 1 })); // true
console.log(isEqual({ a: 1 }, { a: 1, b: 2 })); // false

参考：https://github.com/shfshanyue/Daily-Question/issues/614#issuecomment-886135655