Easier way to have RegExp.test() return false for null values?
let regex = /[a-z]+/;
regex.test('a'); // true
regex.test(''); // false
regex.test(null); // true
regex.test(undefined); // true
So based on this link, Is it a bug in Ecmascript - /S/.test(null) returns true?, it looks like the null value is coerced to a string 'null'. WTF? Why on earth is this designed this way? I also can't find any documentation on this behavior. Is there a way to return false for null/undefined values (without hardcoding in checks for 'null', etc.)?
The argument of RegExp.test() is expected to be a string. If it isn't, it is converted to a string:
var regex = /[object Object]/;
console.log(regex.test({})); // trueIf you're testing a variable, you could do:
regex.test(var || '')
so that it will default to the empty string if it's not set.
You can override test method.
old = regex.test
regex.test = function(str){
str = str? str: "";
return old.call(this, str);
}
regex.test(null); // false
One way is to get your expected output is to check the value first and replace it with "" empty string in case of null or undefined
let regex = /[a-z]+/;
function test (inp){
return regex.test(inp? inp: '');
}
test(null); // false
test(undefined); // false