【Javascript】IE下substr()函数截取末尾字符时的问题

    这两天刚遇到一个问题,substr()函数在IE和FF下表现不一致,导致了一个IE下的bug。

    可以通过以下代码来测试:

    提示:你可以先修改部分代码再运行。

    希望得到的是c,FF下表现正常;但跑到IE下,显示abc,不是期望的结果。看来IE在处理substr()第一个参数为负数的情况处理方式不一样。

    为了解决问题,另觅蹊径,改用substring()函数代替substr()



    提示:你可以先修改部分代码再运行。

    p.s. 附一篇学习文章:substr() vs substring() vs slice()

    substr()

    substr() method extracts a specified number of characters in a string, from a start index.

    Syntax: string.substr(start, length);

    Quick Notes aout Substr:

    • If start is negative, Internet Explorer returns the whole string. That’s wrong! IE should use the last character in the string.

    substring()

    substring() method extracts the chars in a string between two specified indexes.

    Syntax: string.substring(start, stop);

    Quick Notes about Substring:

    • If start equals stopit returns an empty string.
    • If stop is omitted, it extracts characters to the end of the string.
    • If either argument is less than 0 or is NaN, it is treated as if it were 0.
    • If either argument is greater than string’s length, either argument will use string’s length.
    • If start > stop, then substring will swap those 2 arguments

    slice()

    slice() works like substring() with a few different behaviors.

    Syntax: string.slice(start, stop);

    Quick Notes about Slice:

    • If stop is omitted, slice extracted chars to the end of the string, exactly like substring().
    • If start > stop, slice() will NOT swap the 2 arguments.
    • If start is negative, slice() will set char from the end of string, exactly like substr() in Firefox. This behavior is observed in both Firefox and IE.
    • If stop is negative, slice() will set stop to: (string.length – 1) – stop (original value).

    参考:Javascript: substr() v.s. substring()



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