JavaScript List

function List() {
    this.listSize = 0;
    this.pos = 0;
    this.dataSource = [];
    this.clear = function() {
        this.dataSource = [];
        this.pos = 0;
        this.listSize = 0;
    };
    this.find = function(item) {
        for (var i = this.dataSource.length - 1; i >= 0; i--) {
            if (this.dataSource[i] === item) {
                return i;
            }
        };
        return -1;
    }
    this.toString = function() {
        return this.dataSource;
    };
    this.insert = function(item) {
        var insertPos = this.find(item);
        if (insertPos > -1) {
            this.dataSource.splice(insertPos + 1, 0, item);
            ++this.listSize;
            return true;
        }
        return false;
    };
    this.append = function(item) {
        this.dataSource[this.listSize++] = item;
    };
    this.remove = function(item) {
        var foundAt = this.find(item);
        if (foundAt > -1) {
            this.dataSource.splice(foundAt, 1);
            --this.listSize;
            return true;
        }
        return false;
    };
    this.front = function() {
        this.pos = 0;

    };
    this.end = function() {
        this.pos = this.listSize - 1;
    };
    this.prev = function() {
        if (this.pos > 0) {
            --this.pos;
        }
    };
    this.next = function() {
        if (this.pos < this.listSize - 1) {
            ++this.pos;
        }
    };
    this.length = function() {
        return this.listSize;
    };
    this.currPos = function() {
        return this.pos;
    };
    this.moveTo = function(position) {
        this.pos = position;
    };
    this.getElement = function() {
        return this.dataSource[this.pos];
    };
    this.contains = function(item) {
        for (var i = this.dataSource.length - 1; i >= 0; i--) {
            if (this.dataSource[i] === item) {
                return true;
            }

        };
        return false;
    };
}


var list = new List();
list.append("shidengyun");
list.append("zhujing");
list.append("shidengyun");
list.append("zhujing");

console.log(list.toString());
console.log('-------------');

list.insert("shidengyun");

console.log(list.toString());
console.log('-------------');

list.remove("zhujing");
console.log(list.toString());
console.log('-------------');

list.front();
console.log(list.getElement());
list.next();
console.log(list.getElement());
list.prev();
console.log(list.getElement());
console.log('-------------');
for (list.front(); list.currPos < list.length(); list.next()) {
    console.log(list.getElement());
}
console.log('-------------');
for (list.end(); list.currPos >= 0; list.prev()) {
    console.log(list.getElement());
}