simple-lru.js
function (entry) {
      // update most number to key
      if (entry.index !== this._head - 1) {
        var isTail = entry.index === this._tail;
        delete this._byOrder[entry.index];
        entry.index = this._head++;
        this._byOrder[entry.index] = entry;
        if (isTail) this._shift();
      }
    }
function (entry) {
      // update most number to key
      if (entry.index !== this._head - 1) {
        var isTail = entry.index === this._tail;
        delete this._byOrder[entry.index];
        entry.index = this._head++;
        this._byOrder[entry.index] = entry;
        if (isTail) this._shift();
      }
    }
function ( entry ) { // update most number to key if ( entry . index !== this . _head - 1 ) { var isTail = entry . index === this . _tail ; delete this . _byOrder [ entry . index ] ; entry . index = this . _head ++ ; this . _byOrder [ entry . index ] = entry ; if ( isTail ) this . _shift ( ) ; } }
update least recently used index of an entry to "_head"

@param {Entry}
@api private
update least recently used index of an entry to _head