javascript - How to accumulate poll values ​​when the object code values ​​in the array are the same

var arr = [

<code>    {"code": "a", "poll": 7},
    {"code": "b", "poll": 2},
    {"code": "c", "poll": 18},
    {"code": "a", "poll": 5},
    {"code": "c", "poll": 12},
    {"code": "a", "poll": 1}
];
</code>

var arr2 = [

<code>{"code": "a", "poll": 13},
{"code": "b", "poll": 2},
{"code": "c", "poll": 30}</code>

];
How to achieve the transformation from arr → to arr1, and the code value is not only a b c, but also adsdsd dsdsd a223, any value. How to achieve a similar transformation

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var arr = [

<code>    {"code": "a", "poll": 7},
    {"code": "b", "poll": 2},
    {"code": "c", "poll": 18},
    {"code": "a", "poll": 5},
    {"code": "c", "poll": 12},
    {"code": "a", "poll": 1}
];
</code>

var arr2 = [

<code>{"code": "a", "poll": 13},
{"code": "b", "poll": 2},
{"code": "c", "poll": 30}</code>

];
How to realize the transformation from arr → to arr1, and the code value is not only a b c, but also adsdsd dsdsd a223, any value. How to realize a similar transformation