window.prompt() shows a dialog with a text field and waits for OK or Cancel (MDN). OK returns a string; Cancel returns null.
Pass the required arguments shown below. Check return values and browser support before you rely on the result.
Call window.prompt. Start with this line.
prompt() / prompt(msg) / prompt(msg, def)| Call | What it does |
|---|---|
prompt() / prompt(msg) / prompt(msg, def) | Primary signature. |
window.prompt(...) | Call with the arguments your case needs. |
Built into the browser. Call window.prompt(...) (or the global prompt(...)) — no import required.
prompt() / prompt(msg) / prompt(msg, def)| Parameter | Description |
|---|---|
| message | Optional. Text shown above the input |
| defaultValue | Optional. Pre-filled input text |
| Return Value | Description |
|---|---|
| * | string or null |
Pre-fill the field, then greet on OK.
const userName = prompt("Please enter your name:", "Guest");
if (userName === null) {
console.log("Canceled");
} else {
console.log("Hello, " + userName + "!");
}null first.Three outcomes: cancel, blank OK, or typed text.
const userInput = prompt("Enter something:");
if (userInput === null) {
console.log("Canceled");
} else if (userInput === "") {
console.log("OK but empty");
} else {
console.log("Entered:", userInput);
}prompt. No default this time.null first. Cancel is not the same as blank.alertCombine prompt input with an alert message.
const name = prompt("What is your name?");
if (name !== null && name.trim() !== "") {
alert("Nice to meet you, " + name + "!");
} else {
alert("No name provided.");
}prompt result.alert for a simple reply.Re-prompt until a positive number is entered, or stop on Cancel.
let age;
do {
age = prompt("Enter your age (positive number):");
if (age === null) break;
} while (age.trim() === "" || isNaN(Number(age)) || Number(age) <= 0);
if (age !== null) {
console.log("Valid age:", age);
} else {
console.log("Canceled");
}null. Cancel exits cleanly.Number and reject blanks / NaN / ≤ 0.Ask with a default and write the answer into the page.
const color = prompt("What is your favorite color?", "Blue");
if (color === null) {
console.log("No color chosen.");
} else {
console.log("Favorite color:", color);
}null means no choice.Window.prompt() is marked Baseline Widely available on MDN (since July 2015). Browser Window API — not a Node.js built-in.
Ask for text with a modal dialog across modern browsers.
Bottom line: Fine for learning and quick demos. Prefer forms or
Change a window’s size by a relative pixel amount.
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