I'm curious to know how this code is extracting parameters from the website URL. Can someone walk me through the process step by step?

I needed to extract parameters from a URL and started searching online for solutions. I came across a helpful link that provided the information I was looking for:

After visiting the website, I found this code snippet:

function getUrlVars() {
    var vars = {};
    var parts = window.location.href.replace(/[?&]+([^=&]+)=([^&]*)/gi, function(m,key,value) {
        vars[key] = value;
    });
    return vars;
}

The code worked perfectly for my needs, but I wasn't entirely sure about how it achieved the desired result. Specifically, I was curious about the use of \1 and \2 in the function's parameter.

If someone could kindly explain the step-by-step process behind this code, especially regarding the parameter 'm', I would greatly appreciate it.

Answer №1

When using the .replace method, the second argument can actually be a function. This function will have access to the full matched string as its first parameter, followed by any capture groups that were used in the regular expression. For instance, if there are multiple capture groups, each subsequent one will correspond to an argument in the function.

But what about the first parameter 'm' - what's its purpose?

The initial parameter represents the entire match and is typically not utilized. However, it must still be declared in order to make use of the subsequent arguments (such as capture groups) within the function.

In this scenario, the value stored in key will correspond to the substring captured by the specified group:

([^=&]+) (which captures any characters except for = and & in the query string)

Similarly, the content of value will reflect the substring caught by the designated group:

([^&]*) (representing the associated value in the query string, consisting of zero or more characters excluding &)

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