Range Over Built in TypeScript

Here we use `for...of` to sum the numbers in an array. Arrays work like this too.

```typescript
let nums: number[] = [2, 3, 4];
let sum: number = 0;

for (let num of nums) {
    sum += num;
}
console.log("sum:", sum);

for...of on arrays and slices provides the value for each entry. Sometimes we actually want the indexes though.

for (let i = 0; i < nums.length; i++) {
    let num = nums[i];
    if (num === 3) {
        console.log("index:", i);
    }
}

for...in on an object iterates over key/value pairs.

let kvs: { [key: string]: string } = { "a": "apple", "b": "banana" };

for (let k in kvs) {
    let v = kvs[k];
    console.log(`${k} -> ${v}`);
}

for...in can also iterate over just the keys of an object.

for (let k in kvs) {
    console.log("key:", k);
}

for...of on a string iterates over Unicode code points. The first value is the rune itself.

for (let [i, c] of [..."go"].entries()) {
    console.log(i, c.charCodeAt(0));
}

$ ts-node range-over-built-in-types.ts
sum: 9
index: 1
a -> apple
b -> banana
key: a
key: b
0 103
1 111

Next example: Pointers.

Recursion in TypeScript

Pointers in TypeScript

Learn X By Example

Title here

Range Over Built in TypeScript