Iterate Over an Object

To iterate over all properties in an object, we can use the loop for...in... to iterate over the keys:

The syntax:

for (let key in object) {
  // do something for each key in the object 
}

Example:

let fruits = {'apple':'red', 'pear':'green', 'banana':'yellow', 'plum':'purple'}

for (let k in fruits) {
    console.log(k + ' is ' + fruits[k])
}

Console result:

apple is red
pear is green
banana is yellow
plum is purple

Here in the for loop, variable k receives the keys of object fruits ('apple', 'pear'...). Then fruits[k] is used to access the value paired with the key k.

Demo Objects in CodeCraft

We can use an object to store column color and height values to build columns.

Example:

let collection = {'box_red': 10, 'box_green': 6, 'box_blue': 8, 'box_pink': 2};

let x = 0;
for (let m in collection) {
  console.log(m);
  column(x, -20, collection[m], m);
  x += 2;
}

See console result:

box_red
box_green
box_blue
box_pink