点击运行
let DEFAULT_VAL = 30 function addTwoNumbers(first,second = DEFAULT_VAL){ console.log('first parameter is :',first) console.log('second parameter is :',second) return first+second; } console.log("case 1 sum",addTwoNumbers(1)) console.log("case 2 sum",addTwoNumbers(3,undefined))
运行结果 :
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