ArrayFill.js

Array.prototype.fill = function fill(value,start=0, end=this.length) {
  /*
    Every element of array from start up to but not including end are assigned value.
    start and end are interpretation the same as for slice,
        negative start or stop indices are converted to positive indices relative to the lenth of the array.
        
    
    If end<=start no elements are modified.
    If end>this.length and this.length is read-only a range error is thrown and no elements are modified.
    If end>this.length and this.length is not read-only, this.length is set to end.
    Array elements are set sequntially starting with the start index.
    If an element is encountered that cannot be assigned, a type error is thrown and no other elements are modified

    The array is return as the value of this method
*/
  //the following is not yet complete
  var t = Object(this);
  var len = Math.max(0,Math.trunc(t.length));
  var relativeStart = 
           if (this == null) {
            throw new TypeError();
        }

        var n = 0;
        if (arguments.length > 1) {
            n = Number(arguments[1]);
            if (n != n) { // shortcut for verifying if it's NaN
                n = 0;
            } else if (n != 0 && n != Infinity && n != -Infinity) {
                n = (n > 0 || -1) * Math.floor(Math.abs(n));
            }
        }