Question

我的递归函数正在破坏，我无法弄清楚为什么。我正在尝试使用准系统javascript为json编写一个解析器，并且似乎无法解决为什么我的函数不起作用。任何人都可以帮我一把吗？

在css中，你会得到一些元素，这些元素是你用这样的

来解决的特定元素的子元素

#nav li{
  some style here
}

尝试在javascript中操作相同的东西只是它不起作用。到目前为止，我的代码适用于简单的选择器。

var json = {
    "body" : {
        "background": "#303030",
        "color": "#FFFFFF",
        "font-family": "Arial, Helvetica, sans-serif"
    },
    "#nav": {
        "li": {
            "display": "inline-block",
            "list-styles": "none",
            "margin-right": "10px",
            "padding": "10px, 10px"
        }
    }
}
// How to use:
// json is an obj
// body is a selector
// background is a property belong to a selector
// #303030 is a value for the property


//apply css changes to document without writing any css
//by default the first values are
//               selector = background
//               parent   = document
//               object   = json
function styleApply(selector, parent, object){
    var element, onSelector, signal;

    //checks the first character of the selector and grabs element from page depending on what type of element it is
    switch(selector[0]){
        case ".":
            element= parent.getElementsByClassName(selector.substring(1));
            newParent = element[0]; //checks to see what is in the first index of the obtained element
            break;
        case "#":
            element= parent.getElementById(selector.substring(1));
            newParent = element;
            break;
        default:
            element= parent.getElementsByTagName(selector);
            newParent = element[0];
            break;
    }

    //only works if there is actually an element in the page corresponding with the selector
    if(newParent != null){ 
        //loops through all elements with the same selector or in the case of id just does one loop
        for(var i=0; i<element.length; i++){ 

            //loops through all properties in the selector
            for (var property in object[selector]){
                //grabs the associated value with the selector could be string or object
                var value= object[selector][property];

                //if it is a string it is a style, if it is an object, it is targeting the elements inside the current selector only
                if(typeof(value) === "string"){
                    element[i].style.setProperty(property, value);
                }else{

/*I am breaking my code right here*/

                    //reusing the same function, this time selector is equal to property for the case of nav, it is the element 'li'
                    //newParent is the element who is a parent of the current element (e.g 'nav' is parent of 'li')
                    //value is the new object that is replacing json, 
                    styleApply(property, newParent, value); //since value is an object it did not pass the string test and now the new object is value
/*Problem ends here */


                }
            }
        }
    } 
}

my code for looping over all the values in json
for (var selector in json){
    styleApply(selector, document, json);
}

Answer 1

这是我读到的关于将json解析为css的简短代码，我想尝试一下

- 选择器指的是你在json中编写的css选择器

- 父开始引用文档，如javascript
中的Document对象模型
- object是在
中传递的json对象      如果我误用任何术语，请再次纠正我

function styleApply(selector, parent, object){
    var element, onSelector, signal;

    switch(selector[0]){
        case ".":
            element= parent.getElementsByClassName(selector.substring(1));
            break;
        case "#":
            element= [parent.getElementById(selector.substring(1))];
            break;
        default:
            element= parent.getElementsByTagName(selector);
            break;
    }

    if(element[0] != null){
        for(var i=0; i<element.length; i++){ 
            for (var property in object[selector]){

                var value= object[selector][property];

                if(typeof(value) === "string"){
                    element[i].style.setProperty(property, value);
                }else{
                    styleApply(property, element[i], object[selector]);
                }
            }
        }
    } 
}

Answer 2

我碰巧看着json编写一个更清晰的CSS而不是将字符串和数字连接在一起。我没有将样式直接应用于每个元素，而是将它们放入<style>元素中，这使得在整个页面生命周期中更容易更改。它还能够定位伪元素，例如：之前，我使用过。

无论如何，这是函数：

// convert json to css
function jsonToCss(obj) {
    var x, finalStr=''
    for (x in obj) {
        var y, decStr=''
        for (y in obj[x]) {
            decStr+= y + ':' + obj[x][y] + ';'
        }
        finalStr+= x + '{' + decStr + '}'
    }
    return finalStr
}

由于该函数仅通过两个级别（一个用于选择器，一个用于声明）递归，因此需要按如下方式修改json：

var json = {
    "body" : {
        "background": "#303030",
        "color": "#FFFFFF",
        "font-family": "Arial, Helvetica, sans-serif"
    },
    "#nav li": {
        "display": "inline-block",
        "list-styles": "none",
        "margin-right": "10px",
        "padding": "10px, 10px"
    }
}

将其输入函数并获得以下字符串：

body{background:#303030;color:#FFFFFF;font-family:Arial, Helvetica, sans-serif;}#nav li{display:inline-block;list-styles:none;margin-right:10px;padding:10px, 10px;}

然后您可以将其放入样式元素中。我没有验证函数产生的字符串，看它是否格式正确，但它在我的结尾处工作得很好。

JSON CSS解析器

2 个答案: