How to check if a string “StartsWith” another string in JavaScript ?
In JavaScript, the ‘startsWith()’ method is a built-in method that allows one to check whether a string starts with a specified substring.
Syntax: It takes a single argument, which is the substring we want to check whether the string starts with.
string.startsWith(searchString[, position])
Approach 1: Using startWith method
The ‘searchString’ parameter is the substring that you want to search for at the beginning of the string. The ‘position’ parameter is an optional parameter that specifies the position in the string to start the search. If not specified, the search starts from the beginning of the string (position 0).
Example 1: This example shows the use of the above-explained approach.
const str = 'Hello Beginner!';
console.log(str.startsWith('Hello')); // true
console.log(str.startsWith('Beginner', 6)); // true
console.log(str.startsWith('Beginner', 7)); // false
Output:
true
true
false
Example 2: This example shows the use of the above-explained approach.
let x ="Hello World!"
function myfunc() {
if (x.startsWith('Hello')) {
result = true;
} else {
result = false;
}
console.log(result);
}
myfunc();
Output:
true
Approach 2: Using Regular Expression (RegExp)
Regular expressions provide a flexible way to match patterns within strings. We can use a regular expression pattern to check if a string starts with another string.
function startsWith(str, substr) {
// Escape special characters in the substring
const escapedSubstr = substr.replace(/[.*+?^${}()|[\]\\]/g, '\\$&');
// Create a regular expression pattern to match the start of the string
const pattern = new RegExp('^' + escapedSubstr);
// Test if the string matches the pattern
return pattern.test(str);
}
console.log(startsWith('Hello World', 'Hello')); // Output: true
console.log(startsWith('JavaScript', 'Script')); // Output: false
Output
true false
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