如何確定JSON對象是否具有子項

Question

我有一個通過一些JSON在Angular中構建的菜單，該菜單最大深度為3級。 一些菜單項沒有子級，而其他菜單項進入第二或第三級。 我正在嘗試找出一種方法來確定選定的子類別是否具有任何子元素，如果有，則需要隱藏一個按鈕。

每次選擇一個子類別（如“數字藝術”），該值就會在$ scope.selectedSubMarket;中捕獲。

如何在$ scope.art中檢查帶有cat：Digital Art的對象是否有子對象？ 在JSON的更下方，您會看到像“漫畫”這樣的子類別，它沒有2級，我需要一種方法來檢查它並且沒有運氣。

這是構建菜單的JSON示例：

       $scope.art = [
        {"cat": "Digital Art", "second": [
            {"sub": "3 Dimensional Art", "third": [
                {"desc": "Abstract"},
                {"desc": "Characters"},
                {"desc": "Objects"},
                {"desc": "Scenes"},
                {"desc": "Vehicles"},

            ]},
            {"sub": "Animation", "third": [
                {"desc": "Abstract"},
                {"desc": "Characters"},
                {"desc": "Animals"},
                {"desc": "Fantasy"},
                {"desc": "Graffiti"},
                {"desc": "Illustrations"},
                {"desc": "Landscapes & Scenery"},
                {"desc": "Macabre & Horror"},
                {"desc": "People"},
                {"desc": "Sci-fi"},
                {"desc": "Space Art"},
                {"desc": "Political"},
                {"desc": "Pop Art"},
                {"desc": "Psychedelic"},
                {"desc": "Still Life"},
                {"desc": "Surreal"},
            ]},
            {"sub": "Fractal Art", "third": [
                {"desc": "Fractal Animation"},
                {"desc": "Fractal Manipulation"},
                {"desc": "Raw Fractal"},
            ]},
            {"sub": "Photomanipulation", "third": [
                {"desc": "Abstract"},
                {"desc": "Animals & Plants"},
                {"desc": "Conceptual"},
                {"desc": "Dark"},
                {"desc": "Emotional"},
                {"desc": "Humourous"},
                {"desc": "Landscapes & Scenery"},
                {"desc": "Macabre & Horror"},
                {"desc": "People"},
                {"desc": "Sci-fi"},
                {"desc": "Minimalism"},
                {"desc": "Political"},
                {"desc": "Pop Art"},
                {"desc": "Psychedelic"},
                {"desc": "Surreal"},
            ]},
            {"sub": "Pixel Art"},
            {"sub": "Text Art"},
            {"sub": "Typography"},
            {"sub": "Vector", "third": [
                {"desc": "Abstract"},
                {"desc": "Animals & Plants"},
                {"desc": "Conceptual"},
                {"desc": "Dark"},
                {"desc": "Emotional"},
                {"desc": "Humourous"},
                {"desc": "Landscapes & Scenery"},
                {"desc": "Macabre & Horror"},
                {"desc": "People"},
                {"desc": "Sci-fi"},
                {"desc": "Minimalism"},
                {"desc": "Political"},
                {"desc": "Pop Art"},
                {"desc": "Psychedelic"},
                {"desc": "Surreal"},
            ]},
            {"sub": "Vexel", "third": [
                {"desc": "Abstract"},
                {"desc": "Animals & Plants"},
                {"desc": "Conceptual"},
                {"desc": "Dark"},
                {"desc": "Emotional"},
                {"desc": "Humourous"},
                {"desc": "Landscapes & Scenery"},
                {"desc": "Macabre & Horror"},
                {"desc": "People"},
                {"desc": "Sci-fi"},
                {"desc": "Minimalism"},
                {"desc": "Political"},
                {"desc": "Pop Art"},
                {"desc": "Psychedelic"},
                {"desc": "Surreal"},
            ]},


        ]},
        {"cat": "Traditional Art", "second": [
            {"sub": "Assemblage"},
            {"sub": "Body Art", "third": [
                {"desc": "Body Modification"},
                {"desc": "Cosmetic Application"},
                {"desc": "Tattoos"},
                {"desc": "Scenes"},
                {"desc": "Vehicles"},
            ]},
            {"sub": "Collage"},
            {"sub": "Drawings", "third": [
                {"desc": "Abstract"},
                {"desc": "Technical Drawing"},
                {"desc": "Animals"},
                {"desc": "Fantasy"},
                {"desc": "Portrait & Figures"},
                {"desc": "Illustrations"},
                {"desc": "Landscapes & Scenery"},
                {"desc": "Macabre & Horror"},
                {"desc": "People"},
                {"desc": "Sci-Fi"},
                {"desc": "Space Art"},
                {"desc": "Political"},
                {"desc": "Pop Art"},
                {"desc": "Psychedelic"},
                {"desc": "Still Life"},
                {"desc": "Surreal"},

            ]},
            {"sub": "Installation Art"},
            {"sub": "Scratchboard"},
            {"sub": "Paintings", "third": [
                {"desc": "Abstract"},
                {"desc": "Surreal"},
                {"desc": "Animals"},
                {"desc": "Fantasy"},
                {"desc": "Portrait & Figures"},
                {"desc": "Illustrations"},
                {"desc": "Landscapes & Scenery"},
                {"desc": "Macabre & Horror"},
                {"desc": "People"},
                {"desc": "Sci-Fi"},
                {"desc": "Space Art"},
                {"desc": "Political"},
                {"desc": "Pop Art"},
                {"desc": "Psychedelic"},
                {"desc": "Still Life"},
                {"desc": "Surreal"},
            ]},
            {"sub": "Printing", "third": [
                {"desc": "Collagraph"},
                {"desc": "Dry Point"},
                {"desc": "Etching"},
                {"desc": "Lino"},
                {"desc": "Lithograph"},
                {"desc": "Monotype"},
                {"desc": "Silk Screen"},
                {"desc": "Wood Block"},
            ]},
            {"sub": "Street Art", "third": [
                {"desc": "Freehand Graffiti"},
                {"desc": "Installations"},
                {"desc": "Sketch Design"},
                {"desc": "Stencils"},
                {"desc": "Stickers"},
                {"desc": "Wheatpasting"},
            ]},
            {"sub": "Sculpture", "third": [
                {"desc": "Abstract"},
                {"desc": "Busts(People)"},
                {"desc": "Fantasy"},
                {"desc": "Figurative"},
                {"desc": "Horror"},
                {"desc": "Lego"},
                {"desc": "Models"},
                {"desc": "Surreal"},
            ]},

        ]},
        {"cat": "Literature"},
        {"cat": "Artisan Craft"},
        {"cat": "Cartoons"},
        {"cat": "Comics"},
        {"cat": "Animation"},
        {"cat": "Manga & Anime"},
        {"cat": "Scraps"},
        {"cat": "Anthro"},
        {"cat": "Fan Art"},

    ]

Answer 1

如果我說對了

var element = $scope.art.filter(function (el) {return el["cat"] === "Digital Art";})[0];
if (element.second && element.second.length) {
    // Do something
};

對於子元素，請使用先前代碼中的element ：

var subElement = element["second"].filter(function (el) {return el["sub"] === "Animation";})[0];
if (subElement.third && subElement.third.length) {
    // Do something
};