谁能告诉我为什么在尝试调用此函数时会出错？
[英]Can anyone tell me why I get a error when i try to call this function?
问题描述
<!doctype html>
<html>
<script>
function isNumber(value) {
return typeof (value) != "boolean" && !isNaN(value) && value.length > 0;
}
function minMaxDefrost(value, min, max) {
if (value.length == 0 || value == "-") return value;
if (!isNumber(value)) return value.substring(0, value.length - 1);
console.log("minMaxDefrost called ")
if (parseFloat(value) < min){
return min;
}
else if (parseFloat(value) > max){
return max;
}
else {
return Math.floor(value);
}
}
minMaxDefrost(4, 0, 12);
</script>
</html>
- I use this function in a html keyup function and it works fine but when i try to call it by itself at the start of the code i get the error message Uncaught TypeError: value.substring is not a function
我在 html keyup 函数中使用此函数，它工作正常，但是当我尝试在代码开头自行调用它时，我收到错误消息 Uncaught TypeError: value.substring is not a function - also not when i call this function from the keyup i use "this.value = minMaxDefrost(this.value, -80, 150, 0)也不是当我从 keyup 调用这个函数时，我使用“this.value = minMaxDefrost(this.value, -80, 150, 0)
- im assuming the error has got to do with the this.value but i dont know how to fix it我假设错误与 this.value 有关，但我不知道如何修复它
2 个解决方案
解决方案1
0 已采纳 2021-11-12 03:08:37
isNumber(4) evaluates to false , so you're trying to call a substring method on 4 but that doesn't exist. isNumber(4)计算结果为false ，因此您尝试在4上调用substring方法，但该方法不存在。 Use typeof value === 'number' instead to test if something is a number.使用typeof value === 'number'来测试某个东西是否是数字。 Or better yet, use typeof value === 'string' before treating it like it's definitely a string.或者更好的是，在将它视为绝对是字符串之前使用typeof value === 'string' 。
解决方案2
0 2021-11-12 03:17:58
isNumber doesn't exactly do its job as Mark Hanna suggests.. a better isNumber would be something like isNumber并没有像 Mark Hanna 建议的那样完全完成它的工作......更好的isNumber应该是这样的
function isNumber(num){
let num1=num-0, num2=num-1
return num2!=num1 && !!(num2||num1) && typeof(num)!="object"
//Infinity would fail the test num2!=num1
//Normal non-numbers would fail !!(num2||num1)
//null would fail typeof(null)!="object"
//However, 0, and even "0" will pass this test
}
Here is it returned in the code you gave us这是您提供给我们的代码中返回的
function isNumber(num){ let num1=num-0, num2=num-1 return num2!=num1 && !!(num2||num1) && typeof(num)!="object" //Infinity would fail the test num2!=num1 //Normal non-numbers would fail !!(num2||num1) //null would fail typeof(null)!="object" //However, 0, and even "0" will pass this test } function minMaxDefrost(value, min, max) { if (value.length == 0 || value == "-") return value; if (!isNumber(value)) return value.substring(0, value.length - 1); console.log("minMaxDefrost called ") if (parseFloat(value) < min){ return min; } else if (parseFloat(value) > max){ return max; } else { return Math.floor(value); } } minMaxDefrost(4, 0, 12);
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