String
Toolbox

const single = 'Hello';
const double = "Namaste";
const name = "Asha";
const greeting = `Hi ${name}, you have ${2 + 3} messages`; // backticks fill in values

console.log(greeting);
console.log(name.length);          // how many characters
console.log(name[0], name.at(-1)); // first, and last counting from the end
console.log(name.charAt(10));      // out of range gives an empty string

let word = "cat";
word[0] = "b";                  // ignored: a string cannot be edited in place
console.log(word);

const upper = word.toUpperCase(); // every method gives you a NEW string
console.log(word, upper);

word = "b" + word.slice(1);     // to "change" it, build a new one and reassign
console.log(word);

const email = "asha.k@razornext.com";

console.log(email.includes("@"));            // is it anywhere inside?
console.log(email.startsWith("asha"));       // at the very start?
console.log(email.endsWith(".com"));         // at the very end?
console.log(email.indexOf("."));             // position of the first match
console.log(email.lastIndexOf("."));         // position of the last match
console.log(email.indexOf("#"));             // -1 means not found
console.log(email.toLowerCase().includes("RAZOR".toLowerCase())); // ignore case

const file = "report-2026-09.pdf";

console.log(file.slice(0, 6));      // from 0 up to, not including, 6
console.log(file.slice(-3));        // the last 3 characters
console.log(file.slice(7, -4));     // negative numbers count from the end

const parts = file.split("-");      // cut into an array at every "-"
console.log(parts);
console.log(parts.join(" / "));     // glue an array back into one string

console.log("a,b,,c".split(","));   // empty pieces are kept
console.log([..."abc"]);            // split into single characters

const raw = "   Shree Kumar   ";

console.log(`[${raw.trim()}]`);        // remove spaces at both ends
console.log(`[${raw.trimStart()}]`);   // only at the start
console.log(raw.trim().toUpperCase());
console.log(raw.trim().toLowerCase());

console.log("7".padStart(3, "0"));     // "007": fill on the left
console.log("Total".padEnd(10, ".") + "₹450");
console.log("ab".repeat(3));

const text = "red apple, red car, red door";

console.log(text.replace("red", "blue"));     // only the first match
console.log(text.replaceAll("red", "blue"));  // every match
console.log(text.replace(/red/g, "green"));   // a regex with g also means every match

// the replacement can be a function of what was found
const phone = "call 98765 43210 now";
console.log(phone.replace(/\d/g, (digit, index) => (index < 11 ? "*" : digit)));

console.log("apple" === "apple");       // exact match
console.log("Apple" === "apple");       // case matters
console.log("b" > "a", "B" > "a");      // compares character codes, capitals come first

const names = ["zoya", "Aman", "émile", "Bina"];
console.log([...names].sort());         // plain sort: capitals, then small, then accents
console.log([...names].sort((a, b) => a.localeCompare(b))); // how a person would sort

const same = (a, b) => a.localeCompare(b, undefined, { sensitivity: "base" }) === 0;
console.log(same("Resume", "résumé"));  // ignores case and accents

const word = "hi👋";

console.log(word.length);          // 4, because the emoji takes two slots
console.log([...word].length);     // 3: spread counts real characters
console.log([...word].reverse().join("")); // safe reverse

console.log("A".codePointAt(0));   // the number behind a character
console.log(String.fromCodePoint(65, 66, 128578));

const multi = `line one
line two`;                         // backticks keep line breaks
console.log(multi.split("\n").length);

// clean up what a person typed into a sign up form
const form = { name: "  sHREE kumar sharma ", email: " Shree.S@Mail.com ", phone: "9876543210" };

// 1. title case: trim, split into words, capitalise the first letter of each
const titleCase = (s) =>
  s.trim().toLowerCase().split(/\s+/).map((w) => w[0].toUpperCase() + w.slice(1)).join(" ");

// 2. a short handle from the name
const handle = (s) => "@" + titleCase(s).split(" ").map((w) => w.slice(0, 3)).join("").toLowerCase();

// 3. hide most of the phone number
const mask = (p) => p.slice(-4).padStart(p.length, "•");

const clean = {
  name: titleCase(form.name),
  email: form.email.trim().toLowerCase(),
  handle: handle(form.name),
  phone: mask(form.phone),
};
console.log(clean.handle, clean.phone);
console.log(`${clean.name} <${clean.email}> joined as ${clean.handle}`);