3 回答

TA貢獻(xiàn)1824條經(jīng)驗(yàn) 獲得超6個(gè)贊
我建議您閱讀更多有關(guān)html 表單的內(nèi)容:
function KareAlan() {
?var kare1 = document.getElementById("kare1").value;
?var kare1n = parseInt(kare1, 10)
?document.getElementById("sonuc").innerHTML =
? ?"Result:" + " " + kare1
}
<label for="kare1">Input Number</label><br>
<input type="number" value="5" id="kare1" oninput="KareAlan()"></input>
<h3 id="sonuc"></h3>

TA貢獻(xiàn)1839條經(jīng)驗(yàn) 獲得超15個(gè)贊
使用 !isNaN(number) 檢查數(shù)字。
我們使用 isNaN(),如果不是數(shù)字則返回 true,然后我們否定該語句以獲得一個(gè)如果它是數(shù)字則返回 true 的函數(shù)。

TA貢獻(xiàn)1863條經(jīng)驗(yàn) 獲得超2個(gè)贊
正如其他人指出的那樣,該值NaN是 a number。您需要在運(yùn)行代碼typeof之前進(jìn)行檢查,看看會(huì)發(fā)生什么parse
var theApple = "Apple";
var theNumber = 1234;
console.log(
"log line 1: " + theApple,
parseInt(theApple, 10),
"| typeof: " + typeof(theApple),
"| typeof parsedInt: " + typeof(parseInt(theApple, 10)),
);
console.log(
"log line 2: " + theNumber,
parseInt(theNumber, 10),
"| typeof: " + typeof(theNumber),
"| typeof parsedInt: " + typeof(parseInt(theNumber, 10)),
);
// or simply
console.log("log line 3: ", !isNaN(theApple));
console.log("log line 4: ", !isNaN(theNumber));
// the problem with isNan is a value like this is also a NaN:
console.log("log line 5: ", !isNaN('0.0314E+2'));
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