将数组Javascript中的一项设置为空

Question

After initialing an array, it contains empty elements. I want to set an element back to empty after setting an value. But it doesn't work however I set it to undefined/null.

 var a = Array(20181231); // it will not run. a.forEach(e => {console.log(++i + ' - ' + e);}); var i = 0; a[12] = 12; a[2018] = 2018; // it loop twice a.forEach(e => {console.log(++i + ' - ' + e);}); a[12] = undefined; // expecting one time, but it still loop twice. a.forEach(e => {console.log(++i + ' - ' + e);}); 

Answer 1

You could take the delete operator and remove the element of the array.

 var a = Array(20181231); a.forEach(e => console.log(++i + ' - ' + e)); // no loop var i = 0; a[12] = 12; a[2018] = 2018; a.forEach(e => console.log(++i + ' - ' + e)); // two elements delete a[12]; a.forEach(e => console.log(++i + ' - ' + e)); // one element