带有变量的 Javascript 对象表示法 [英] Javascript Object notation with variable

问题描述

我的 PHP 脚本 specs.php 输出如下:

<预><代码>{高清": {方面": ["1920x1080","1920x1080","1920x1080"],尺寸":["603 KB","265 KB",438 KB"]},中等的": {方面": ["800x530","800x530",800x530"],尺寸":["198 KB","105 KB",152 KB"]},状态":成功"}

使用 jQuery 我加载 JSON 并将其分配给 specs_obj
我可以使用 specs_obj 访问第一项的中等"尺寸".中等大小[0]
如何在点符号中使用变量?

var specs_obj;$.post("specs.php", {},功能(数据){if (data.status == "success") {specs_obj = 数据；writeSizes("中");} 别的 {}}, "json");函数 writeSizes(预设){//测试从第一个文件中获取中等尺寸var size = specs_obj.中等大小[0];//var size = specs_obj.preset.sizes[0];}

解决方案

不能在点表示法中使用变量，但可以使用括号表示法:

var size = specs_obj[preset].sizes[0];

如果 preset 包含字符串medium"，则在功能上等同于:

var size = specs_obj.medium.sizes[0];

My PHP script specs.php outputs the following:

{
    "hd": {
        "dimensions": [
            "1920x1080",
            "1920x1080",
            "1920x1080" 
        ],
        "sizes": [
            "603 KB",
            "265 KB",
            "438 KB" 
        ] 
    },
    "medium": {
        "dimensions": [
            "800x530",
            "800x530",
            "800x530" 
        ],
        "sizes": [
            "198 KB",
            "105 KB",
            "152 KB" 
        ] 
    },
    "status": "success"
}

With jQuery I load in the JSON and assign it to specs_obj
I can access the first item's "medium" "sizes" with specs_obj. medium.sizes[0]
How can I use a variable in the dot notation?

var specs_obj;
$.post("specs.php", {},
    function(data) {
        if (data.status == "success") {
                specs_obj = data;
                writeSizes("medium");
        } else {}
    }, "json"
);

function writeSizes(preset) {
    // test get medium dimensions from first file
    var size = specs_obj. medium.sizes[0];
    // var size = specs_obj.preset.sizes[0];
}

解决方案

You can't use a variable in the dot notation, but you can use brackets notation:

var size = specs_obj[preset].sizes[0];

If preset contains the string "medium", that's functionally identical to:

var size = specs_obj.medium.sizes[0];

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