How to quickly clear a JavaScript Object?

Question

With a JavaScript Array, I can reset it to an empty state with a single assignment:

array.length = 0;

This makes the Array \"appear\" empty

Answer 1

This bugged me for ages so here is my version as I didn't want an empty object, I wanted one with all the properties but reset to some default value. Kind of like a new instantiation of a class.

let object1 = {
  a: 'somestring',
  b: 42,
  c: true,
  d:{
    e:1,
    f:2,
    g:true,
    h:{
      i:"hello"
    }
  },
  j: [1,2,3],
  k: ["foo", "bar"],
  l:["foo",1,true],
  m:[{n:10, o:"food", p:true }, {n:11, o:"foog", p:true }],
  q:null,
  r:undefined
};

let boolDefault = false;
let stringDefault = "";
let numberDefault = 0;

console.log(object1);
//document.write("
");
//document.write(JSON.stringify(object1))
//document.write("
");
cleanObject(object1);
console.log(object1);
//document.write(JSON.stringify(object1));
//document.write("
");

function cleanObject(o) {
  for (let [key, value] of Object.entries(o)) {
    let propType = typeof(o[key]);

    //console.log(key, value, propType);

    switch (propType) {
      case "number" :
        o[key] = numberDefault;
        break;

      case "string":
        o[key] = stringDefault;
        break;

      case "boolean":
        o[key] = boolDefault;    
        break;

      case "undefined":
        o[key] = undefined;   
        break;

      default:
        if(value === null) {
            continue;
        }

        cleanObject(o[key]);
        break;
    }
  }
}

// EXPECTED OUTPUT
// Object { a: "somestring", b: 42, c: true, d: Object { e: 1, f: 2, g: true, h: Object { i: "hello" } }, j: Array [1, 2, 3], k: Array ["foo", "bar"], l: Array ["foo", 1, true], m: Array [Object { n: 10, o: "food", p: true }, Object { n: 11, o: "foog", p: true }], q: null, r: undefined }
// Object { a: "", b: 0, c: undefined, d: Object { e: 0, f: 0, g: undefined, h: Object { i: "" } }, j: Array [0, 0, 0], k: Array ["", ""], l: Array ["", 0, undefined], m: Array [Object { n: 0, o: "", p: undefined }, Object { n: 0, o: "", p: undefined }], q: null, r: undefined }