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How do I turn an array of JavaScript objects into an URL string with only one loop?

January 9, 2023

I am trying to turn an array of JavaScript objects into a URL string with params, as seen below:

const objects = [{
    firstName: "John",
    lastName: "Doe",
    age: 46
  },
  {
    country: "France",
    lastName: "Paris"
  }
]

let entry_arr = [];

objects.forEach(obj => {
  Object.entries(obj).forEach(entry => {
    entry_arr.push(entry.join('='));
  });
});

let entry_str = entry_arr.join('&');

console.log(entry_str);

By all appearances, the above code works. There is a problem though.

The problem

As you can see, I have 2 nested forEach loops. For better performance, I wish I knew how to avoid this nesting and instead use only one forEach loop.

How can I achieve the same result with inly one loop?

>Solution :

At least, you need to map the entries with joining key and value and join the nested entries and outer array.

const
    objects = [{ firstName: "John", lastName: "Doe", age: 46 }, { country: "France", lastName: "Paris" }],
    result = objects
        .map(object => Object
            .entries(object)
            .map(entry => entry.join('='))
            .join('&')
        )
        .join('&');

console.log(result);