input range 怎样让滑过的部分变色

<input type="range" min="0" max="50000" step="100" value="0">

input[type="range"] {
    display: block;
    -webkit-appearance: none;
    background-color: #bdc3c7;
    width: 100%;
    height: 2px;
    border-radius: 2px;
    margin: 0 auto;
    outline: 0;
}
input[type="range"]:before{
    content: '';
    width: 10px;
    height: 3px;
    background-color: blue;
}

input[type="range"]::-webkit-slider-thumb {
    position: relative;
    -webkit-appearance: none;
    background-color: #e74c3c;
    width: 20px;
    height: 20px;
    border-radius: 50%;
    border: 2px solid white;
    cursor: pointer;
    transition: 0.3s ease-in-out;
    -webkit-box-shadow: 0 1px 1px black inset;
}

js:

 var elem = document.querySelector('input[type="range"]');
            var rangeValue = function(){
                var newValue = elem.value;
                var target = document.querySelector('.value');
                target.innerHTML = newValue;
            };
            elem.addEventListener("input", rangeValue);

想要实现