How to get the size of an array in an object with JavaScript?

To get the size of an array in an object with JavaScript, we use the length property.

For instance, we write

const st = {
  itemA: {},
  itemB: [
    { id: "s01", cd: "c01", dd: "d01" },
    { id: "s02", cd: "c02", dd: "d02" },
  ],
};

console.log(st.itemB.length);

to get the length of the st.itemB array property with st.itemB.length.