您应该将 \ n 替换为< br> ，因为 innerHTML 接受一个HTML字符串（在HTML中， \ n 与相邻空格合并，但除了样式 white-space：预包装，如MaxArt所述）：

You should replace \n by <br> since innerHTML takes an HTML string (in HTML, \n merges with adjacent spaces but does not produce a carriage return except for elements with the style white-space:pre-wrap as noted by MaxArt) :

document.getElementById("overlaycontent").innerHTML = (
    StringContent.a + '<br>' +
    StringContent.b + '<br>' +
    StringContent.c,
)