js 数组赋值操作,修改数组元素的值

function toTree(rows){  

    function exists(rows, parentId){  
        for(var i=0; i<rows.length; i++){  
            if (rows[i].id == parentId) return true;  
        }  
        return false;  
    }  

    var nodes = [];  
     for(var i=0; i<rows.length; i++){  
        var row = rows[i];  
        if (!exists(rows, row.parentId)){  
            nodes.push({  
                id:row.id,  
                text:row.text,
                state:'closed'
            });  
        }  
    }  

    var toDo = []; 

    //如下的for循环 是把nodes数组对象的引用赋值给了toDo ,功能类似:toDo = nodes; 下面的操作修改了node的值,其实是修改了nodes中的元素的值. 
    for(var i=0; i<nodes.length; i++){  
        toDo.push(nodes[i]);  
    } 
    while(toDo.length){
        var node = toDo.shift();
         for(var i=0; i<rows.length; i++){  
            var row = rows[i];  
            if (row.parentId === node.id){
                var child = {id:row.id,text:row.text,attributes:{href:row.href}};
//              alert(JSON.stringify(node.children));
                if (node.children){
                    node.children.push(child);  
                } else {  
                    node.children = [child];
                }  
                toDo.push(child);
            }  
        }  
    }  
    return nodes; //最终结果是nodes的内容变化了. 
}