Regular expression method function checkRate(input){var re = /^[0-9]+.?[0-9]*$/; //Judge whether the string is a number//Judge Positive integer/^[1-9]+[0-9]*]*$/ if (!re.test(input.rate.value)){alert("Please enter a number (example: 0.02)");input .rate.focus();return false;}}The following is the general...