Question

我希望从第二个位置给我4个字符。但不是。

<body id = "A">
<script>
var s = document.getElementById("A");
var d = "Hello, world";
s.innerHTML = d.substring(2,4);
</script>

它适用于：

d.substring(0,4);

Answer 1

substring的参数是开始和结束，而不是开始和结束。

string.substring(start,end)
Parameter Values
Parameter   Description
start   Required. The position where to start the extraction. First character is at index 0
end     Optional. The position (up to, but not including) where to end the extraction. If omitted, it extracts the rest of the string

有一个加法函数substr，其参数为start和length

string.substr(start,length)
Parameter Values
Parameter   Description
start   Required. The position where to start the extraction. First character is at index 0
length  Optional. The number of characters to extract. If omitted, it extracts the rest of the string

您可以see more at "W3Schools" here ..您可能会发现这是您遇到的其他问题的有用参考。

Answer 2

您需要substr()

var s = document.getElementById("A");
var d = "Hello, world";
s.innerHTML = d.trim().substr(2,4);

Fiddle

substr()和substring()是不同的方法！

Javascript：切片和子串不按预期工作

2 个答案:

Fiddle