将html输入框格式化为仅数字输入 - 正确格式化减号

Question

I'm trying to format a html text input box so that it only accepts numeric values (using javascript). This means the input can only be a digit, a minus or a dot/comma (a comma gets replaced with a dot anyway).

The thing is, a minus must be prevented if it is not the first character of the string. Ex: "-30" is a valid input, but "80----20" is not. Does anyone has any idea on how to solve this?

 var div = document.getElementById("div"); function inputHandle(event, object){ var input = document.getElementById("value"); var comma = false; for (i=0; i<input.value.length; i++) { var array = input.value; if (input.value[i] == ".") { comma = true; } } if ((event.keyCode == 13) && (Number(input.value) < Number.MAX_SAFE_INTEGER)) { object.innerHTML = Number(input.value); } if ((event.charCode == 44) && (comma == false)) { input.value = input.value + "."; event.preventDefault(); } if (!((/^-?\\d*\\.?\\d*$/.test(event.key) == true) || (((event.charCode == 118) || (event.charCode == 99) || (event.charCode == 97)) && (event.ctrlKey)) || (event.keyCode == 8) || (event.keyCode == 46) || (event.keyCode >= 35 && event.keyCode <= 40) )) { event.preventDefault(); } if ((event.charCode == 46) && (comma == true)) { event.preventDefault(); } } 

 <div id="div"></div> <input type='text' onkeypress='inputHandle(event, div)' accept-charset='ISO-8859-1' id='value' name='coefficientvalue' placeholder='Enter a value...'> 

Answer 1

If you really need a input[type="text"] I think a regular expression is the best you could use. The following Regex should work:

/^-?\d*\.?\d*$/

You could check the input value on each input-event with this regex like the following:

/^-?\d*\.?\d*$/.test(input.value)

Otherwise you should use type="number" for your input element, like Andreas commented.

After testing the input you should use parseFloat to normalize the input, since the Regex would allow inputs like ".2" or "2.".