Javascript regex all names starting with

Question

I have a javascript function which should populate a select box with all items from an array starting with the letter passed to the function. The only problem I have is that I can't get my regex statement/coding to work. Here is my function:

function replaceCompanySelect (letter)
{

var list = document.getElementById("company");  //Declare the select box as a variable
list.options.length=0;  //Delete the existing options

list.options[0]=new Option("Please Select a Company", "0", false, false); //Add the first option in

for(var i=1;i<companies.length;i++)  //For each company in the array
{

    if(companies[i].match("/\b"+letter+"/g") != null && (letter != 'undefined' ||letter != 'undefined'))  //If the company starts with the correct letter and the position's value is not undefined or empty
    {

        alert(companies[i]); //Only used for testing purposes, code should be as above loop to I used to insert the 1st option

    }

}

}

Any ideas?

Answer 1

这也可以，并且没有RegEx也可以：

if (companies[i].charAt(0).toLowerCase() == letter.toLowerCase()) {...}

Answer 2

This is actually probably more efficient to do without regular expressions (granted, this would count as micro-optimization though...). I would just do something like:

if (letter && companies[i][0].toLowerCase() === letter.toLowerCase()) { ... }

Answer 3

I wouldn't bother with a regex. You'll just create problems. Something like this would work.

var companies  = ["microsoft","apple","google"],
    startsWith = function(arr,match){

        var length = arr.length;

        for(var i=0; i < length; i+=1){

            if(arr[i].toUpperCase().lastIndexOf(match.toUpperCase(), 0) === 0){

                return arr[i];                           
            }

        }
    };

console.log(startsWith(companies,"g")); //=> returns google

Answer 4

Something like?

function foo (letter) {
 var companies  = ["microsoft","apple","google"];
  return companies.filter(function(s) { return s.match(new RegExp(letter,"ig")); });
}

alert(foo("G")); //google