Here you go:
1) To limit 50 characters set max_length=50 in the attribute section for that catalog variable. so no need for regular expression for this.
2) Have onChange Catalog Client script to validate the values are number, dash, underscore etc. on that variable.
function onChange(control, oldValue, newValue, isLoading, isTemplate) {
if (isLoading || newValue === '') {
return;
}
var validate = new RegExp('^[a-zA-Z0-9-_]+$');
// a-zA-Z means letter
// 0-9 means allow numbers
// - and _ means allow this characters
// try giving value with length as less than 50 and special character such as @ or ! and it should throw the alert message and clear the variable
var result = validate.test(newValue);
if(!result)
{
// value is invalid show alert message and clear the variable
alert('Please give only letters, numbers, dashes, and underscores');
g_form.clearValue('<variableName>'); // add variable name here
}
}
Mark Correct if this solves your issue and also hit Like and Helpful if you find my response worthy based on the impact.
