JavaScript Program to Check Whether a String Starts and Ends With Certain Characters

Example 1: Check String Using Built-in Methods

// program to check if a string starts with 'S' and ends with 'G'

function checkString(str) {

    // check if the string starts with S and ends with G
    if(str.startsWith('S') && str.endsWith('G')) {
        console.log('The string starts with S and ends with G');
    }
    else if(str.startsWith('S')) {
        console.log('The string starts with S but does not end with G');
    }
     else if(str.endsWith('G')) {
        console.log('The string starts does not with S but end with G');
    }
    else {
        console.log('The string does not start with S and does not end with G');
    }
}


// take input
let string = prompt('Enter a string: ');
checkString(string);

Output

Enter a string: String
The string starts with S but does not end with G

In the above program, the two methods startsWith() and endsWith() are used.

• The startsWith() method checks if the string starts with the particular string.
• The endsWith() method checks if the string ends with the particular string.

The above program does not check for lowercase letters. Hence, here G and g are different.

You could also check if the above character starts with S or s and ends with G or g.

str.startsWith('S') || str.startsWith('s') && str.endsWith('G') || str.endsWith('g');

Example 2: Check The String Using Regex

// program to check if a string starts with 'S' and ends with 'G'

function checkString(str) {

    // check if the string starts with S and ends with G
    if( /^S/i.test(str) && /G$/i.test(str)) {
        console.log('The string starts with S and ends with G');
    }
    else if(/^S/i.test(str)) {
        console.log('The string starts with S but does not ends with G');
    }
     else if(/G$/i.test(str)) {
        console.log('The string starts does not with S but ends with G');
    }
    else {
        console.log('The string does not start with S and does not end with G');
    }
}

// for loop to show different scenario
for (let i = 0; i < 3; i++) {

    // take input
    const string = prompt('Enter a string: ');

    checkString(string);
}

Output

Enter a string: String
The string starts with S and ends with G
Enter a string: string
The string starts with S and ends with G
Enter a string: JavaScript
The string does not start with S and does not end with G

In the above program, a regular expression (RegEx) is used with the test() method to check if the string starts with S and ends with G.

• The /^S/i pattern checks if the string is S or s. Here, i denotes that the string is case-insensitive. Hence, S and s are considered the same.
• The /G$/i patterns checks if the string is G or g.
• The if...else...if statement is used to check the conditions and display the outcome accordingly.
• The for loop is used to take different inputs from the user to show different cases.