JavaScript中你不知道的Object.entries用法

const obj = { foo: 'bar', baz: 42 };
console.log(Object.entries(obj)); // [ ['foo', 'bar'], ['baz', 42] ]

// array like object
const obj = { 0: 'a', 1: 'b', 2: 'c' };
console.log(Object.entries(obj)); // [ ['0', 'a'], ['1', 'b'], ['2', 'c'] ]

// array like object with random key ordering
const anObj = { 100: 'a', 2: 'b', 7: 'c' };
console.log(Object.entries(anObj)); // [ ['2', 'b'], ['7', 'c'], ['100', 'a'] ]

// getFoo is property which isn't enumerable
const myObj = Object.create({}, { getFoo: { value() { return this.foo; } } });
myObj.foo = 'bar';
console.log(Object.entries(myObj)); // [ ['foo', 'bar'] ]

// non-object argument will be coerced to an object
console.log(Object.entries('foo')); // [ ['0', 'f'], ['1', 'o'], ['2', 'o'] ]

// iterate through key-value gracefully
const obj = { a: 5, b: 7, c: 9 };
for (const [key, value] of Object.entries(obj)) {
  console.log(`${key} ${value}`); // "a 5", "b 7", "c 9"
}

// Or, using array extras
Object.entries(obj).forEach(([key, value]) => {
console.log(`${key} ${value}`); // "a 5", "b 7", "c 9"

let obj = {
  a: 1,
  b: 2
}

for (let value of obj) {
  // ...
}

for (let key in obj) {
  if (Object.prototype.hasOwnProperty.call(obj, key)) {
    // ...
  }
}

for (let [key, value] of Object.entries(obj)) {
  // ...
}

let obj = {
  a: 1,
  b: 2
}

let map = new Map();

for (let key in obj) {
  if (Object.prototype.hasOwnProperty.call(obj, key)) {
    map.set(key, obj[key]);
  }
}

let map = new Map(Object.entries(obj));

let obj = Object.fromEntries(map);