Strings are a sequence of zero or more characters written inside quotes used to represent text.
Strings may consist of letters, numbers, symbols, words, or sentences.
Strings are immutable, they cannot be changed.
Each character in a string has an index.
The first character will be index 0 the second character will be index 1 and so on.
There are two ways to access an individual character in a string.
charAt() method
const str1 = "abc"; string
str1.charAt(0); character at index 0 → "a"
str1.charAt(1); character at index 1 → "b"
str1.charAt(2); character at index 2 → "c"
str1.charAt(3); character at index 3 → "" index not found
Alternatively use at() or slice() methods
bracket notation []
const str2 = "abc"; string
str2[0]; character at index 0 → "a"
str2[1]; character at index 1 → "b"
str2[2]; character at index 2 → "c"
str2[3]; character at index 3 → undefined index not found
Numbers are used to represent both integer and floating-point values.
Numbers are most commonly expressed in literal forms like 255 or 3.14159 ↴
let num1 = 5; → number
let num2 = 2.5; → number
let num3 = num1 + num2;
console.log(num3); returns ↴
7.5 → number
Generate a chess pattern using a for loop
for loop repeatedly executes a block of code until a specified condition evaluates to false.
The loop runs a block of code a set number of times, defined by an initialization, a condition, and an increment.
for (let x = 0; x < 4; x++) {
console.log(x);
}
Loop variable x is initialized to 0
Condition x < 4 is checked before each iteration.
The loop will continue to run as long as x is less than 4
The loop repeatedly executes a block of code 4 times, from 0 to 3
For each iteration of the loop, the current value of x is printed to the console.
After each iteration, x is incremented by 1 x++
When x reaches 4 the condition evaluates to false, terminating the loop.
0
1
2
3 → printed to console
Modulo operator % (remainder operator) returns the remainder left over when one number is divided by a second number.
10 % 2 → remainder 0
10 % 3 → remainder 1
10 % 4 → remainder 2
10 % 5 → remainder 0
The modulo operator can be used to check whether a number is odd or even.
If a number is divisible by 2 (with no remainder) then it must be an even number.
If a number is not divisible by 2 (with a remainder) then it must be an odd number.
4 % 2 === 0; statement is true, remainder is zero, so 4 is an even number.
5 % 2 === 0; statement is false, remainder is not zero, so 5 is an odd number.
function checkNumber(num) {
if (num % 2 === 0) { if num divisible by 2
console.log(num + " is even"); if true
} else {
console.log(num + " is odd"); if false
}
};
checkNumber(2); → 2 is even
checkNumber(3); → 3 is odd
checkNumber(4); → 4 is even
checkNumber(5); → 5 is odd
Initialize a variable to hold the character to be used to represent the dark squares of the chess board.
const char = "x" char → user input
Initialize a variable to hold the grid size of the chess board (number of rows/columns).
const grid = 8 grid → user input
Define a function chessBoard() to generates a chess board pattern.
function chessBoard(char, num) {}
The function takes a string character char and a number num to generate a chess board pattern.
Initialize an empty string to build the chess board.
let board = ""
The function uses nested loops to create a 2D grid.
The outer loop iterates through the rows, while the inner loop iterates through the columns.
The chessboard pattern is achieved by alternating between a space and the specified character based on the sum of the current row and column indices.
Loop through each row of the grid y
for (let y = 0; y < grid; y++) {}
Loop through each column of the grid x
for (let x = 0; x < grid; x++) {}
A conditional statement, using the modulus operator, % determines whether to append a space or the character based on the current indices.
Check if the sum of the current row and column indices is even.
if ((x + y) % 2 == 0) {}
If even, add a space to the board " "
board += " "
Else if odd, add the specified character char to the board.
board += char
After completing a row, add a newline character to move to the next row.
board += "\n"
The board is built as a string, which is printed to the console.
console.log(board)
Call the function with ↴
chessBoard(char, grid);
Generate a chess board pattern with character "x" and a 8 × 8 grid.
const char = "x"; → character
const grid = 8; → grid
let board = "";
function chessBoard(char, grid) {
for (let y = 0; y < grid; y++) {
for (let x = 0; x < grid; x++) {
if ((x + y) % 2 == 0) {
board += " ";
} else {
board += char;
}
}
board += "\n";
}
console.log(board);
}
call function
chessBoard(char, grid); returns ↴
x x x x
x x x x
x x x x
x x x x
x x x x
x x x x
x x x x
x x x x
→ printed to console