JS in the original test pattern is a string JS detecting the presence or absence, JS determines whether the input value is a positive integer codes: <script type=”text/javascript”> function test() { var num = document.getElementById(“num”).value; if (num==”") { alert ( 'Enter content'); return false; } if (!(/(^[1-9]\d*$)/.test(num))) { alert ( 'input is not a positive integer'); return false; }else { alert ( 'input is a positive integer'); } } </script> <html> <body> <input type=”text” id=”num” /> <input type=”button” value=”测试” onclick=”return test()” /> </body> </html> Analyzing attached figures, floating-point regular expression: "^ \\ d + $" // non-negative integer (integer + 0) "^ [0-9] * [1-9] [0-9] * $" // positive integer "^ ((- \\ d +) | (0 +)) $" // non-positive integer (negative integer + 0) "^ - [0-9] * [1-9] [0-9] * $" // negative integer "^ -? \\ d + $" // integer "^ \\ d + (\\. \\ d +)? $" // non-negative floating-point numbers (positive float + 0) . "^ (([0-9] + \\ [0-9] * [1-9] [0-9] *) | ([0-9] * [1-9] [0-9] * \\ [0-9] +) |. ([0-9] * [1-9] [0-9] *)) $ "// positive 浮点 number "^ ((- \\ d + (\\ \\ d +)) |.?.? (0 + (\\ 0 +))) $" // non-positive float (negative float + 0) "^? (-? \\ d +) (. \\ \\ d +) $" // float
Beginning with a non-zero integer or decimal
/^[1-9][0-9]*([.][0-9]+)?$/
Non-zero integer beginning or two decimal places
/^[1-9][0-9]*([.][0-9]{1,2})?$/
/^[1-9][0-9]*([.][0-9]{2})?$/