distanceConverter

function attachEventsListeners() {
    let inputToMeters = {
        km: (input) => input * 1000,
        m: (input) => input * 1,
        cm: (input) => input / 100,
        mm: (input) => input / 1000,
        mi: (input) => input * 1609.34,
        yrd: (input) => input * 0.9144,
        ft: (input) => input * 0.3048,
        in: (input) => input * 0.0254,
    };

    let outputUnits = {
        km: (n) => n / 1000,
        m: (n) => n / 1,
        cm: (n) => n * 100,
        mm: (n) => n * 1000,
        mi: (n) => n / 1609.34,
        yrd: (n) => n / 0.9144,
        ft: (n) => n / 0.3048,
        in: (n) => n / 0.0254,
    };

    let inputUnit = document.getElementById("inputUnits");
    let inputNum = document.getElementById("inputDistance");

    let outUnit = document.getElementById("outputUnits");
    let outNum = document.getElementById("outputDistance");

    let convBtn = document.getElementById("convert");
    convBtn.addEventListener("click", onClick);

    function onClick() {
        let inUn = inputUnit.value;

        let inN = Number(inputNum.value);

        let outUn = outUnit.value;

        let inNtoM = inputToMeters[inUn](inN);

        outNum.value = outputUnits[outUn](inNtoM);
    }
}