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<title>Document</title>
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<script>
let arr = [1,3,55,8];
// 需求：arr数组中的所有小于5的值翻倍并求和
let count = arr.filter(function(n){
return n < 5;
}).map(function(n){
return n*2;
}).reduce(function(preValue, n){
return preValue + n;
},0);
console.log(`和：${count}`);
</script>
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