AlgoDaily - Implement JSON.parse - One Pager Cheat Sheet

One Pager Cheat Sheet

You can implement your own version of the JSON.parse() method, called parseJSON, that accepts one parameter and can return one of the following: array, object, string, number, boolean, or null.
By defining multiple if cases to check for null, empty objects, arrays or booleans and additional parsing of values inside quotes and brackets, we can create a JSON Parser in JavaScript.

This is our final solution.

To visualize the solution and step through the below code, click Visualize the Solution on the right-side menu or the VISUALIZE button in Interactive Mode.

xxxxxxxxxx
}
 
function parseJSON(input) {
​
    // if the input is empty or starts with an invalid character, throw an error
    if (input === "" || input[0] === "'") {
        throw Error();
    }
​
    // check if the input is null, an empty object, empty array, or a boolean and return the value from the input
    if (input === "null") {
        return null;
    }
    if (input === "{}") {
        return {};
    }
    if (input === "[]") {
        return [];
    }
    if (input === "true") {
        return true;
    }
    if (input === "false") {
        return false;
    }
​
    //if the input starts with a quote, return the value from inside the quotes
    if (input[0] === '"') {
        return input.slice(1, -1);
    }
​
    // if it starts with a bracket, perform parsing of the contents within the brackets
    if (input[0] === "{") {
        return input

That's all we've got! Let's move on to the next tutorial.

If you had any problems with this tutorial, check out the main forum thread here.