javascript - 从 javascript litteral 获取第一个对象

Question

假设我这里有这个对象:

var items = [
    {name:"Foo"},
    {name:"Bar"},
    {name:"foo"},
    {name:"bar"},
    {name:"foobar"},
    {name:"barfoo"}
];

由于每个对象中只有一个项目，因此我只想返回它们的列表。

我尝试过这个:

var getSingle = function(rows){
    var items = [];
    //This should only return one column
    for (var i = 0; i < rows.length; i++) {
        var r = rows[i];
        var c = 0;
        for (var n in r) {
            if(c == 0)
                items.push(r[n]);
            c += 1;
        }
    }
    return items;
}

但是好像不行。有什么想法吗？

PS。 name 可以是任何东西。

Answer 1

我使用了与其他人不同的方法，因为我做了两个假设:

1/你不知道键的名称，但每个项目只有一个键2/每个项目的 key 可以不同我会给你第二个选择，第二个假设是:2/所有项目只有一个 key ，但对所有项目来说都是相同的

第一个选项:

var items = [
        {name:"Foo"},
        {name:"Bar"},
        {name:"foo"},
        {name:"bar"},
        {name:"foobar"},
        {name:"barfoo"}
    ];

// object keys very simple shim
Object.keys = Object.keys || function(o) {  
    var result = [];  
    for(var name in o) {  
        if (o.hasOwnProperty(name))  
          result.push(name);  
    }  
    return result;  
};

// function to get the value of every first keys in an object
// just remember that saying "first key" does not make real sense
// but we begin with the assumption that there IS ONLY ONE KEY FOR EVERY ITEM
// and this key is unknown
function getFirstKeysValues(items) {
    var i = 0, len = items.length, item = null, key = null, res = [];
    for(i = 0; i < len; i++) {
        item = items[i];
        key = Object.keys(item).shift();
        res.push(item[key]);
    }

    return res;
}

console.log(getFirstKeysValues(items)); //["Foo", "Bar", "foo", "bar", "foobar", "barfoo"]

第二个选项将使用 map ，因为我们相信每个 child 都拥有相同的 key (我不会使用这个，因为我不太喜欢 .map - 兼容性):

var items = [
        {name:"Foo"},
        {name:"Bar"},
        {name:"foo"},
        {name:"bar"},
        {name:"foobar"},
        {name:"barfoo"}
    ];

// object keys very simple shim
Object.keys = Object.keys || function(o) {  
    var result = [];  
    for(var name in o) {  
        if (o.hasOwnProperty(name))  
          result.push(name);  
    }  
    return result;  
};

// function to get the value of every first keys in an object
// just remember that saying "first key" does not make real sense
// but we begin with the asumption that there IS ONLY ONE KEY FOR EVERY ITEM
// and this key is unknown but the same for every child
function getFirstKeysValues(items) {
    var key = items.length > 0 ? Object.keys(items[0]).shift() : null;

    items = items.map(function (item) {
        return item[key];
    });

    return items;
}

console.log(getFirstKeysValues(items));