JavaScript function to compare strings

Question

I've written this function for to check if two strings are equal.

Can I improve it?

Is there a better way to accomplish the task?

// Compares two Strings concerning equality.

// -- Parameter --------------------------------
// 1. String - The string to compare against.
// 2. String - The string to compare with.

// -- Return -----------------------------------
// Boolean - True if both string are equal.

function compareSrings(firstString, secondString) {
  if ( firstString === undefined || 
       secondString === undefined ) return;
  
  var needle = new RegExp('^' + secondString + '$');
  
  return (firstString.length === secondString.length) && 
         (firstString.search(needle) === 0);
}
// --- TEST -----------------------------------------

var first = [ 'Test',
              'Demo',
              '123',
              'Alpha',
              'Beta',
              'Gamma',
              'Delta Epsilon',
              'Rot Gelb Grün Blau',
              'javaScript',
              '$Demo123',
              '',
              'xyz'
            ];
var second = [ 'Test',
              'Demo',
              '1234',
              'Alpha',
              'beta',
              'Gamma',
              'Delta psilon',
              'Rot Gelb Grün Blau',
              '',
              'somethingElse',
              ''
            ];
 
for (var i = 0; i < first.length; i++) {
  console.log( '%s === %s => %s', 
               first[i],
               second[i],
               compareSrings(first[i], second[i]));  
}

200_success · Accepted Answer · 2016-02-12 09:08:37Z

4

It's weird that if either string is undefined, then the function returns neither true nor false, but undefined.

What you wrote is not a string equality checker; it's a regular expression matcher. If secondString contains any special regular expression characters (like a $), then the test falls apart.

You could fix that problem by escaping the regex. But that seems silly, when you could just use firstString === secondString to check for equality.

answered Feb 12, 2016 at 9:08

200_success

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