How to iterate over Object’s property-value pairs?

An answer to your Question from 2019:

It depends on what version of ECMAScript you use.

Pre ES6:

Use any of the answers below, e.g.:

for (var m in myMap){
    for (var i=0;i<myMap[m].length;i++){
    ... do something with myMap[m][i] ...
    }
} 

For ES6 (ES 2015):

You should use a Map object, which has the entries() function:

var myMap = new Map();
myMap.set("0", "foo");
myMap.set(1, "bar");
myMap.set({}, "baz");

for (const [key, value] of myMap.entries()) {
  console.log(key, value);
}

For ES8 (ES 2017):

Object.entries() was introduced:

const object = {'a': 1, 'b': 2, 'c' : 3};
for (const [key, value] of Object.entries(object)) {
  console.log(key, value);
}