string.match() returns a String instead of an Array

Elie Zgala

I've been using Javascript string.match(*regex*) function to parse the navigator.userAgent string.

FYI, According to MDN & W3schools:

"The match() method searches a string for a match against a regular expression, and returns the matches, as an Array object."

I first parse once to get the wanted strings for the base string:

var userAgent = navigator.userAgent;
var splitted = userAgent.match(/[(][^)]+[)]|\w+\/\S+/ig);

Which gives me the following Output (Which is an Array)

Mozilla/5.0
(Macintosh; Intel Mac OS X 10_10_3)
AppleWebKit/537.36
(KHTML, like Gecko)
Chrome/41.0.2272.76
Safari/537.36

Then i parse the Navigator/Version type strings in a for loop

for (var i = 0; i < splitted.length; i++ ) {
    var str = splitted[i];
    if (str[0] == '(') {
    } else {
        var name = str.match(/[^\/]+/i);
        var version = str.match(/[0-9|\.]+/i);
}

But, very surprisingly and even though I get the desired result, I get a String Object for the name and an Array Object for the version

How is it even possible ?

Here's the snippet of the code (fiddle):

var userAgent = navigator.userAgent;
var splitted = userAgent.match(/[(][^)]+[)]|\w+\/\S+/ig);
var outputDiv = document.getElementById("log");

for (var i = 0; i < splitted.length; i++ ) {
  var str = splitted[i];
  if (str[0] == '(') {
  } else {
    var name = str.match(/[^\/]+/i);
    var version = str.match(/[0-9|\.]+/i);
    outputDiv.innerHTML += name.toString() + " is a " + typeof(name) + "<br>";
    outputDiv.innerHTML += version.toString() + " is a " + typeof(version) + "<br>";
  }
};

<div id="log"></div>

--- UPDATE ---

Thanks FactoryAidan for the answer, it was a scope problem.

Conclusion: be careful when naming global variables :)

FactoryAidan

Global Variable Scope

It is because you are using name as your variable. This is a global browser window variable that is inherently a string and cannot be stored as an Array

Even if you redeclare it with var name =, you are still in the global scope. And thus name (aka window.name) simply retains the last value you assign to it.

You can test this with the following on an empty page without defining any variables at all:

console.log(name===window.name) // Returns true
console.log(name,window.name)   // Returns 'Safari Safari' for my browser

Change `name` to something else

If you change your name variable to simply have a different name, like my_name, it stores the result of .match() as an Array.

var my_name = str.match(/[^\/]+/i);
var version = str.match(/[0-9|\.]+/i);

console.log(typeof my_name, my_name instanceof Array) // Returns object, true

Change Scope by wrapping in a function

This is your exact code wrapped inside a function and returns the correct variable types:

function getBrowserStuff(){

    var userAgent = navigator.userAgent;
    var splitted = userAgent.match(/[(][^)]+[)]|\w+\/\S+/ig);

    for (var i = 0; i < splitted.length; i++ ) {
        var str = splitted[i];
        if (str[0] == '(') {
        } else {
            var name = str.match(/[^\/]+/i);
            var version = str.match(/[0-9|\.]+/i);
            console.log('Name','Typeof '+(typeof name), 'IsArray '+(name instanceof Array),name)
            console.log('Version','Typeof '+(typeof version),'IsArray '+(version instanceof Array),version)
        }
    }

    return 'whatever'
}

getBrowserStuff()

Changing the variable name to my_name OR wrapping code like the above function returns this:

Name    Typeof object IsArray true ["Mozilla"]
Version Typeof object IsArray true ["5.0"]
Name    Typeof object IsArray true ["AppleWebKit"]
Version Typeof object IsArray true ["600.3.18"]
Name    Typeof object IsArray true ["Version"]
Version Typeof object IsArray true ["8.0.3"]
Name    Typeof object IsArray true ["Safari"]
Version Typeof object IsArray true ["600.3.18"]

Where before it returned this:

Name    Typeof string IsArray false Mozilla
Version Typeof object IsArray true  ["5.0"]
Name    Typeof string IsArray false AppleWebKit
Version Typeof object IsArray true  ["600.3.18"]
Name    Typeof string IsArray false Version
Version Typeof object IsArray true  ["8.0.3"]
Name    Typeof string IsArray false Safari
Version Typeof object IsArray true  ["600.3.18"]

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edited at2020-10-22

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