前置“http://"到不包含“http://"的 URL； [英] Prepending "http://" to a URL that doesn't already contain "http://"

问题描述

我有一个保存 URL 的 input 字段，我希望这个保存的输入能够识别变量开头何时不存在Http//"但不知道从哪里开始...是否可以只检查字符串的一部分?- 然后有一个函数可以在必要时追加?

解决方案

您想要的简单解决方案如下:

var prefix = 'http://';if (s.substr(0, prefix.length) !== prefix){s = 前缀 + s；}

但是，您应该注意一些事项...

这里的测试区分大小写.这意味着如果字符串最初是 Http://example.com 这会将其更改为 http://Http://example.com 这可能不是什么你要.您可能也不应该修改任何以 foo:// 开头的字符串，否则最终可能会得到类似 http://https://example.com 的内容.>

另一方面，如果您收到诸如 example.com?redirect=http://othersite.com 之类的输入，那么您可能确实希望在 http:// 所以仅仅搜索 :// 对于通用解决方案来说可能不够好.

替代方法

• 使用正则表达式:

  if (!s.match(/^[a-zA-Z]+:///)){s = 'http://' + s;}

• 使用 URI 解析库，例如 JS-URI.

  if (new URI(s).scheme === null){s = 'http://' + s;}

相关问题

• Javascript equalsIgnoreCase:不区分大小写的字符串比较
• javascript 开始
• 我如何解析一个URL 到主机名和 javascript 路径?

I have an input field that saves a URL, I'd like this saved input to recognize when "Http//" is absent from the start of the variable but have no idea where to begin... is it possible to check only a portion of a string? - then have a function that will append if necessary?

解决方案

A simple solution for what you want is the following:

var prefix = 'http://';
if (s.substr(0, prefix.length) !== prefix)
{
    s = prefix + s;
}

However there are a few things you should be aware of...

The test here is case-sensitive. This means that if the string is initially Http://example.com this will change it to http://Http://example.com which is probably not what you want. You probably should also not modify any string starting with foo:// otherwise you could end up with something like http://https://example.com.

On the other hand if you receive an input such as example.com?redirect=http://othersite.com then you probably do want to prepend http:// so just searching for :// might not be good enough for a general solution.

Alternative approaches

• Using a regular expression:

  if (!s.match(/^[a-zA-Z]+:///))
  {
      s = 'http://' + s;
  }
  

• Using a URI parsing library such as JS-URI.

  if (new URI(s).scheme === null)
  {
      s = 'http://' + s;
  }
  

Related questions

• Javascript equalsIgnoreCase: case insensitive string comparation
• javascript startswith
• How do I parse a URL into hostname and path in javascript?

这篇关于前置“http://"到不包含“http://"的 URL；的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！