js遍历json数据计算，对比另一条json,组成表格

//有两条json数据a和b,如下图：
//a的json中有一个fruit数组和stationery数组（可以为空），里面有名称和数量。
//b的json中对应的类型和特征
//需求：根据a和b,计算水果数量，组成如下表格。
//这种json对象里套数组有点懵，组成表格时，需要取a,b重新组成新的json吗？
谢谢.

var a = [{
                "id": "1548208772510",
                "area": "上海",
                "fruit": [{
                    "fname": "苹果",
                    "fnum": 4
                }],
                "stationery": [],
            },
            {
                "id": "1548208889319",
                "area": "上海",
                "fruit": [],
                "stationery": [{
                        "sname": "钢笔",
                        "snum": 5
                    },
                    {
                        "sname": "毛笔",
                        "snum": 4
                    }
                ]
            },
            {
                "id": "1548208889319",
                "area": "上海",
                "fruit": [{
                    "fname":"橘子",
                    "fnum": 3
                }
                ],
                "stationery": [{
                        "sname": "钢笔",
                        "snum": 1
                    },
                    {
                        "sname": "毛笔",
                        "snum": 9
                    }
                ]
            }
        ];

var b = [
        {
            "id": "1548208889389",
            "type": '水果',
            "name": '苹果',
            "feature": '又圆又甜'
        },
        {
            "id": "1548208889387",
            "type": '水果',
            "name": '橘子',
            "feature": '又圆又酸'
        },
        {
            "id": "1548208889317",
            "type": '文具',
            "name": '毛笔',
            "feature": '流畅'
        },
        {
            "id": "1548208889387",
            "type": '文具',
            "name": '钢笔',
            "feature": '帅气'
        }
        ];

你的b对象中type属性有重名。我改变了一下

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
<script>
var a = [{
                "id": "1548208772510",
                "area": "上海",
                "fruit": [{
                    "fname": "苹果",
                    "fnum": 4
                }],
                "stationery": [],
            },
            {
                "id": "1548208889319",
                "area": "上海",
                "fruit": [],
                "stationery": [{
                        "sname": "钢笔",
                        "snum": 5
                    },
                    {
                        "sname": "毛笔",
                        "snum": 4
                    }
                ]
            },
            {
                "id": "1548208889319",
                "area": "上海",
                "fruit": [{
                    "fname":"橘子",
                    "fnum": 3
                }
                ],
                "stationery": [{
                        "sname": "钢笔",
                        "snum": 1
                    },
                    {
                        "sname": "毛笔",
                        "snum": 9
                    }
                ]
            }
        ];

var b = [
        {
            "id": "1548208889389",
            "type": '水果',
            "name": '苹果',
            "feature": '又圆又甜'
        },
        {
            "id": "1548208889387",
            "type": '水果',
            "name": '橘子',
            "feature": '又圆又酸'
        },
        {
            "id": "1548208889317",
            "type": '文具',
            "name": '毛笔',
            "feature": '流畅'
        },
        {
            "id": "1548208889387",
            "type": '文具',
            "name": '钢笔',
            "feature": '帅气'
        }
    ];
</script>

<table border="1">
    <tr>
        <th>类型</th>
        <th>名称</th>
        <th>数量</th>
        <th>特征</th>
    </tr>
<script type="text/javascript">
var numbers = {};
a.forEach(function(n1){
    n1.fruit.forEach(function(n2){
        numbers[n2.fname] = (numbers[n2.fname]||0) + n2.fnum;
    });
    n1.stationery.forEach(function(n2){
        numbers[n2.sname] = (numbers[n2.sname]||0) + n2.snum;
    });
});
b.forEach(function(obj){
    document.write('<tr><td>'+obj.type+'</td><td>'+obj.name+'</td><td>'+numbers[obj.name]+'</td><td>'+obj.feature+'</td></tr>');
});
</script>
</table>

</html>

<!DOCTYPE html>
<html>

    <head>
        <meta charset="UTF-8">
        <title></title>
    </head>

    <body>
            hahahahahhahahahahaah
    </body>
    <script>
         let a = [
            {
                "id": "1548208772510",
                "area": "上海",
                "fruit": [
                    {
                        "fname": "苹果",
                        "fnum": 4
                    }
                ],
                "stationery": [],
            },
            {
                "id": "1548208889319",
                "area": "上海",
                "fruit": [],
                "stationery": [
                    {
                        "sname": "钢笔",
                        "snum": 5
                    },
                    {
                        "sname": "毛笔",
                        "snum": 4
                    }
                ]
            },
            {
                "id": "1548208889319",
                "area": "上海",
                "fruit": [
                    {
                        "fname":"橘子",
                        "fnum": 3
                    }
                ],
                "stationery": [
                    {
                        "sname": "钢笔",
                        "snum": 1
                    },
                    {
                        "sname": "毛笔",
                        "snum": 9
                    }
                ]
            }
        ]; 
        let b = [
            {
                "id": "1548208889389",
                "type": '水果',
                "name": '苹果',
                "type": '又圆又甜'
            },
            {
                "id": "1548208889387",
                "type": '水果',
                "name": '橘子',
                "type": '又圆又酸'
            },
            {
                "id": "1548208889317",
                "type": '文具',
                "name": '毛笔',
                "type": '流畅'
            },
            {
                "id": "1548208889387",
                "type": '文具',
                "name": '钢笔',
                "type": '帅气'
            }
        ];
        //遍历b,给b的每一项新增number、arr属性
        for(var i = 0; i < b.length;i++){
            b[i].number = 0;
            b[i].arr = [];
        }

        for(var i = 0; i < a.length;i++){
            for(var j = 0;j < a[i].fruit.length;j++){
                //把水果抽出来push到跟b里面一样名字的水果的arr中
                for(k = 0; k < b.length;k++){
                    if(a[i].fruit[j].fname == b[k].name){
                        b[k].arr.push(a[i].fruit[j]);
                    }
                }
            }
            for(var j = 0;j < a[i].stationery.length;j++){
                //把文具抽出来push到跟b里面一样名字的文具的arr中
                for(k = 0; k < b.length;k++){
                    if(a[i].stationery[j].sname == b[k].name){
                        b[k].arr.push(a[i].stationery[j]);
                    }
                }
            }
        }

        //然后再遍历b计算各自水果的数量
        for(var i = 0;i < b.length;i++){
            //遍历每一项的arr
            var num = 0;
            for(var j = 0; j < b[i].arr.length;j++){
                if(b[i].arr[j].fnum){
                    num += b[i].arr[j].fnum
                }
                if(b[i].arr[j].snum){
                    num += b[i].arr[j].snum
                }
            }
            b[i].number = num;
        }
        console.log('打印b你就会看到水果和文具全部抽出啦放到b里面去了,并且已经计算好了数量',b);
    </script>

</html>