9. Strings – JavaScript Programs
1. Find String Length
Methods used: .length
Program 1: Direct Length
<script>
let s = "JavaScript";
document.write(s.length);
</script>
Program 2: Using Function
<script>
function getLength(s) {
return s.length;
}
document.write(getLength("Programming"));
</script>
Program 3: Length After Removing Spaces
<script>
let s = "Java Script";
document.write(s.replaceAll(" ", "").length);
</script>
2. Reverse a String
Methods used: .length, indexing, .split(), .reverse(), .join()
Program 1: Using Loop
<script>
let s = "hello";
let rev = "";
for (let i = s.length - 1; i >= 0; i--) {
rev += s[i];
}
document.write(rev);
</script>
Program 2: Using Predefined Methods
<script>
let s = "JavaScript";
document.w
</script>
Program 3: Function Based
<script>
function reverseStr(s) {
return s.split("").reverse().join("");
}
document.write(reverseStr("coding"));
</script>
3. Check Palindrome String
Methods used: .split(), .reverse(), .join(), .toLowerCase()
Program 1: Simple Palindrome Check
<script>
let s = "madam";
let rev = s.split("").reverse().join("");
document.write(s === rev ? "Palindrome" : "Not Palindrome");
</script>
Program 2: Case-Insensitive Palindrome
<script>
let s = "Level";
let str = s.toLowerCase();
document.write(str === str.split("").reverse().join("") ? "Palindrome" : "Not");
</script>
Program 3: Using Function
<script>
function isPalindrome(s) {
s = s.toLowerCase();
return s === s.split("").reverse().join("");
}
document.write(isPalindrome("Radar"));
</script>
4. Count Vowels and Consonants
Methods used: .toLowerCase(), .includes()
Program 1: Using Loop
<script>
let s = "javascript";
let v = 0, c = 0;
for (let i = 0; i < s.length; i++) {
let ch = s[i].toLowerCase();
if (ch >= 'a' && ch <= 'z') {
if ("aeiou".includes(ch)) v++;
else c++;
}
}
document.write("Vowels: " + v + ", Consonants: " + c);
</script>
Program 2: Using Regex
<script>
let s = "programming";
let vowels = s.match(/[aeiou]/gi).length;
let consonants = s.match(/[bcdfghjklmnpqrstvwxyz]/gi).length;
document.write(vowels + " " + consonants);
</script>
5. Convert String to Uppercase / Lowercase
Methods used: .toUpperCase(), .toLowerCase()
Program 1: Uppercase
<script>
let s = "javascript";
document.write(s.toUpperCase());
</script>
Program 2: Lowercase
<script>
let s = "JAVASCRIPT";
document.write(s.toLowerCase());
</script>
Program 3: Toggle Case
<script>
let s = "JavaScript";
let result = "";
for (let ch of s) {
result += ch === ch.toUpperCase()
? ch.toLowerCase()
: ch.toUpperCase();
}
document.write(result);
</script>
6. Count Words in a String
Methods used: .split(), .trim()
Program 1: Using split
<script>
let s = "JavaScript is easy";
document.write(s.split(" ").length);
</script>
Program 2: Handling Extra Spaces
<script>
let s = " Learn JavaScript Now ";
document.write(s.trim().split(/\s+/).length);
</script>
Program 3: Manual Count
<script>
let s = "Practice makes perfect";
let count = 1;
for (let i = 0; i < s.length; i++)
if (s[i] === " ") count++;
document.write(count);
</script>
7. Replace a Word in a String
Methods used: .replace(), .replaceAll()
Program 1: Replace First Occurrence
<script>
let s = "I like JS";
document.write(s.replace("JS", "JavaScript"));
</script>
Program 2: Replace All Occurrences
<script>
let s = "JS is fast. JS is popular.";
document.write(s.replaceAll("JS", "JavaScript"));
</script>
Program 3: Using Regex
<script>
let s = "apple apple apple";
document.write(s.replace(/apple/g, "orange"));
</script>
8. Check Substring Existence
Methods used: .includes(), .indexOf(), .search()
Program 1: Using includes
<script>
let s = "JavaScript";
document.write(s.includes("Script"));
</script>
Program 2: Using indexOf
<script>
let s = "Programming";
document.write(s.indexOf("gram") !== -1 ? "Found" : "Not Found");
</script>
Program 3: Using search
<script>
let s = "Hello World";
document.write(s.search("World") >= 0);
</script>
9. Capitalize First Letter of Each Word
Methods used: .split(), .charAt(), .slice(), .toUpperCase()
Program 1: Using split
<script>
let s = "java script language";
let words = s.split(" ");
let result = "";
for (let w of words) {
result += w.charAt(0).toUpperCase() + w.slice(1) + " ";
}
document.write(result);
</script>
Program 2: Without split
<script>
let s = "learning javascript";
let res = "";
let cap = true;
for (let ch of s) {
if (cap && ch !== " ") {
res += ch.toUpperCase();
cap = false;
} else {
res += ch;
}
if (ch === " ") cap = true;
}
document.write(res);
</script>
10. Remove Spaces from String
Methods used: .replace(), .replaceAll(), .split(), .join(), .trim()
Program 1: Remove All Spaces
<script>
let s = "Java Script Basics";
document.write(s.replaceAll(" ", ""));
</script>
Program 2: Remove Leading & Trailing Spaces
<script>
let s = " Hello World ";
document.write(s.trim());
</script>
Program 3: Using split & join
<script>
let s = "Remove all spaces";
document.write(s.split(" ").join(""));
</script>
A. Programs using for…in with String
(for…in iterates over indexes)
Program 1. Print Each Character with Index
<script>
let str = "JavaScript";
for (let i in str) {
document.write("Index " + i + " : " + str[i] + "<br>");
}
</script>
Program 2. Count Characters in a String
<script>
let str = "Programming";
let count = 0;
for (let i in str) {
count++;
}
document.write("Length: " + count);
</script>
Program 3. Reverse a String using for…in
<script>
let str = "hello";
let rev = "";
for (let i in str) {
rev = str[i] + rev;
}
document.write(rev);
</script>
Program 4. Count Vowels using for…in
<script>
let str = "javascript";
let vowels = 0;
for (let i in str) {
if ("aeiou".includes(str[i])) {
vowels++;
}
}
document.write("Vowels: " + vowels);
</script>
B. Programs using for…of with String
(for…of iterates over characters directly – best for strings)
Program 5. Print Each Character
<script>
let str = "Coding";
for (let ch of str) {
document.write(ch + "<br>");
}
</script>
Program 6. Count Vowels and Consonants
<script>
let str = "education";
let v = 0, c = 0;
for (let ch of str) {
if ("aeiou".includes(ch)) v++;
else c++;
}
document.write("Vowels: " + v + "<br>Consonants: " + c);
</script>
Program 7. Reverse a String using for…of
<script>
let str = "hello";
let rev = "";
for (let ch of str) {
rev = ch + rev;
}
document.write(rev);
</script>
Program 8. Check Palindrome using for…of
<script>
let str = "madam";
let rev = "";
for (let ch of str) {
rev = ch + rev;
}
document.write(str === rev ? "Palindrome" : "Not Palindrome");
</script>
Program 9. Remove Spaces using for…of
<script>
let str = "Java Script Basics";
let result = "";
for (let ch of str) {
if (ch !== " ") result += ch;
}
document.write(result);
</script>
C. Programs using forEach with String
(forEach works after converting string → array)
Program 10. Print Each Character using forEach
<script>
let str = "Hello";
str.split("").forEach(function(ch) {
document.write(ch + "<br>");
});
</script>
Program 11. Count Vowels using forEach
<script>
let str = "javascript";
let count = 0;
str.split("").forEach(ch => {
if ("aeiou".includes(ch)) count++;
});
document.write("Vowels: " + count);
</script>
Program 12. Convert String to Uppercase using forEach
<script>
let str = "hello";
let result = "";
str.split("").forEach(ch => {
result += ch.toUpperCase();
});
document.write(result);
</script>
Program 13. Reverse String using forEach
<script>
let str = "coding";
let rev = "";
str.split("").forEach(ch => {
rev = ch + rev;
});
document.write(rev);
</script>
Program 14. Count Words using forEach
<script>
let str = "JavaScript is very easy";
let count = 0;
str.split(" ").forEach(word => {
if (word !== "") count++;
});
document.write("Words: " + count);
</script>
D. Comparison Program (Very Important for Learners)
Program 15. Same Task using All Three Loops
<script>
let str = "Loop";
// for...in
for (let i in str) document.write(str[i] + " ");
document.write("<br>");
// for...of
for (let ch of str) document.write(ch + " ");
document.write("<br>");
// forEach
str.split("").forEach(ch => document.write(ch + " "));
</script>