Exploring Nested Loops in TypeScript

Introduction

Our path today leads through the realm of Exploring Nested Loops in TypeScript. Think of these as revolving mechanisms within each other, much like solar systems within galaxies, each having its own distinct motion. We'll delve deep and learn how to efficiently manipulate these loops in TypeScript by the end of this tutorial.

Structure of a Nested for Loop in TypeScript

We'll begin by unveiling the format of a nested for loop in TypeScript:

TypeScript
for (let i = 0; i < 3; i++) {
   for (let j = 0; j < 3; j++) {
       console.log(`i = ${i}, j = ${j}`); // e.g., "i = 0, j = 0"
    }
}
/*
Prints:
i = 0, j = 0
i = 0, j = 1
i = 0, j = 2
i = 1, j = 0
i = 1, j = 1
i = 1, j = 2
i = 2, j = 0
i = 2, j = 1
i = 2, j = 2
*/

For each progression of i from 0 to 2, we run through j from 0 to 2 and display the respective values of i and j.

Structure of a Nested while Loop in TypeScript

Just as with for loops, while loops can also be composed of nested loops:

TypeScript
let i = 0;
while (i < 3) {
    let j = 0;
    while (j < 3) {
        console.log(`i = ${i}, j = ${j}`); // e.g., "i = 0, j = 0"
        j++;
    }
    i++;
}
/*
Prints:
i = 0, j = 0
i = 0, j = 1
i = 0, j = 2
i = 1, j = 0
i = 1, j = 1
i = 1, j = 2
i = 2, j = 0
i = 2, j = 1
i = 2, j = 2
*/

In this case, too, the inner loop j runs in its entirety for every single iteration of the outer loop i.

Iterations and Nested Loops: An Example

To illustrate nested loops, let's observe a two-dimensional (2D) array — essentially an array of arrays:

TypeScript
let matrix: number[][] = [
    [1, 2, 3],
    [4, 5, 6], 
    [7, 8, 9]
];

for (let i = 0; i < matrix.length; i++) {   // Iterating over each row.
    let row = '';
    for (let j = 0; j < matrix[i].length; j++) {  // Iterating over each element in the row.
        row += `${matrix[i][j]} `; 
    }
    console.log(row);
}
/*
Prints:
1 2 3
4 5 6
7 8 9
*/

For every i row (outer loop), an inner loop goes through every element within that row.

Iterations and Nested Loops: Another Example

Here is another example of a nested for loop that creates a numerical pyramid:

TypeScript
for (let i = 1; i <= 5; i++) { // The first loop denotes each level of the pyramid.
    let row = '';
    for (let j = 1; j <= i; j++) { // The second loop adds numbers to each level.
        row += `${j} `;
    }
    console.log(row); // Prints each level of the pyramid.
}

/*
Prints:
1
1 2
1 2 3
1 2 3 4
1 2 3 4 5
*/
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