const m = new Map(); m.set('a1', 1); m.set('a2', 1); m.set('a3', 1); m.set('a4', 1); function fun1(map) { map.forEach((v, k) => { return k; }); } console.log(fun1(m)); // `undefined`
请问如何让他输出 a1 呢?
a1
https://developer.mozilla.org...
用forEach是优雅不了了,可以试下for of
forEach
for of
function fun1(map) { for (const [k, v] of map) { return k; } }
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