[英]How to make sure the user enters a valid number in Javascript?
I'm asking the user to enter a number, so how can I use a loop to make sure they enter a number?我要求用户输入一个数字,那么我如何使用循环来确保他们输入一个数字? If they don't enter a number, I want to prompt the user again for a valid number.
如果他们不输入数字,我想再次提示用户输入有效数字。 Then I would loop the prompt until a valid number is entered.
然后我会循环提示,直到输入一个有效的数字。
var size = prompt('Enter a size');
size = Number(size);
console.log(size);
do { var size = prompt('Enter a size'), isNumber = isNaN(size); !isNumber && console.log(size); } while (isNumber);
function isNumber(n) {
return !isNaN(parseFloat(n)) && isFinite(n);
}
var size = "";
while (!isNumber(size))
size = prompt('Enter a size');;
using: Javascript - validation, numbers only使用: Javascript - 验证,仅限数字
function promptLoop() {
var size = prompt('Enter a size');
size = Number(size);
if (isNaN(size)) {
alert("Must input numbers"); // optional
promptLoop();
}
else console.log(size);
}
Try this examples:试试这个例子:
var size = prompt('Enter a size');
//Test if is integer positive value.
var patron = /^[0-9]+$/;
if (patron.test(size)){
//is a valid.
}
//Test if is integer negative or positive .
patron = /^[-]?[0-9]+$/;
if (patron.test(size)){
//is a valid.
}
//Test if is decimal.
patron = /^[-]?[0-9]+[\.]?[0-9]+$/;
if (patron.test(size)){
//is a valid.
}
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