Javascript正则表达式仅在字符串开头检查数字和减号
[英]Javascript regex to check only numbers and minus at the start of string
问题描述
Hello I am trying to make a regex in this input field to accept only 4 numbers not greater than 2934, but accept a negative one too (-2394). 
您好，我正在尝试在此输入字段中创建一个正则表达式，以仅接受不大于2934的4个数字，但也接受负数（-2394）。
I want to allow the minus sign only at the start of the string, and then 4 numbers only, not greater than 2934 (positive and negative, because they are coordinates. 我只想在字符串的开头允许减号，然后只允许4个数字，不大于2934（正负），因为它们是坐标。
Already tried the given solutions here, but I am missing something. 已经在这里尝试了给定的解决方案，但我错过了一些东西。
function numonly(myfield, e, dec){ // max input value of 4196 x 4196 $("#mlat,#mlon").keyup(function() { var val = $(this).val().replace(/[^0-9]+/,""); if (val => 2934){ !/^\\s*$/.test(val); val = (parseInt(val) > 2934) ? 2934 : val; } else { (!/^\\s*$/.test(val)); val = (parseInt(val) > 2934) ? 2934 : val; } $(this).val(val); }); }
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script> <input id="mlat" type="text" name="mlat" maxlength="4" onkeypress="return numonly(this,event)"><br> <input type="text" name="mlon" id="mlon" maxlength="4" onkeypress="return numonly(this,event)">
3 个解决方案
解决方案1
1 2018-02-22 12:37:39
I am trying to make a regex in this input field to accept only 4 numbers not greater than 2934, but accept a negative one too (-2394).
No need for regex here, use 这里不需要正则表达式，使用
var minValue = -2394;
var maxValue = 2934;
var val = +$(this).val().replace(/[^0-9-]+/g,""); //using your own regex to replace non-numeric characters
var isValid = !isNaN( val ) && val < maxValue && val > minValue ;
Also, i noticed that you want to make these values as upper and lower bound 另外，我注意到您想将这些值作为上限和下限
if ( !isNaN( val ) )
{
var finalVal = isValid ? val : (val < 0 ? minValue : maxValue);
}
解决方案2
0 2018-02-22 13:09:04
function numonly(myfield, e, dec){
// max input value of 4196 x 4196
$("#mlat,#mlon").keyup(function() {
var val = $(this).val().replace(/[^0-9-]+/,"");
if (parseInt(val) > 2934){
val = (parseInt(val) > 2934) ? 2934 : val;
}
else {
val = (parseInt(val) < -2934) ? -2934 : val;
}
$(this).val(val);
});
}
Increase your max length to 5 to cater the '-' 将您的最大长度增加到5以迎合“-”
<input id="mlat" type="text" name="mlat" maxlength="5" onkeypress="return numonly(this,event)"><br>
<input type="text" name="mlon" id="mlon" maxlength="5" onkeypress="return numonly(this,event)">
解决方案3
0 已采纳 2018-02-22 13:10:51
you can use the following method : 您可以使用以下方法：
<html>
<head>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
</head>
<body>
<input id="mlat" type="text" name="mlat" maxlength="5" onkeypress="return numonly(this,event)"><br>
<input type="text" name="mlon" id="mlon" maxlength="5" onkeypress="return numonly(this,event)">
<script type="text/javascript">
function numonly(myfield, e, dec){
// max input value of 4196 x 4196
$("#mlat").keyup(function() {
var val = $(this).val().replace(/-?\d+[^0-9]+/,"");
if (val => 2934){
!/^\s*$/.test(val);
if (val > 0) {
val = (parseInt(val) > 2934) ? 2934 : val;
}else{
val = (parseInt(val) > -2394) ? val : -2394;
}
}
else {
(!/^\s*$/.test(val));
if (val > 0) {
val = (parseInt(val) > 2934) ? 2934 : val;
}else{
val = (parseInt(val) > -2394) ? val : -2394;
}
}
$(this).val(val);
})
};
</script>
</body>
</html>
and replace the maxlength to 5 to handle - sign in input tag. 并将maxlength替换为5以进行处理-登录输入标签。
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