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JavaScript - check if URL is external
9 points
In this short article, we would like to show how using JavaScript, to check if URL is external.
Practical example:
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const ORIGIN_EXPRESSION = /^https?:\/\/[^/?#]+/i;2
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const compareStrings = (a, b) => a.toLowerCase() === b.toLowerCase();4
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const isExternal = (url, origin = location.origin) => {6
if (url == null) { // null or undefined7
return false;8
}9
if (url === '') {10
return false;11
}12
const match = url.match(ORIGIN_EXPRESSION);13
if (match) {14
return !compareStrings(origin, match[0]); // web page origin !== indicated url origin15
}16
return false;17
};18
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// Usage example:21
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console.log(isExternal('')); // false23
console.log(isExternal('/snippets')); // false24
console.log(isExternal('?parameter=value')); // false25
console.log(isExternal('#anchor')); // false26
console.log(isExternal('robots.txt')); // false27
console.log(isExternal('/path/to/file.txt')); // false28
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console.log(isExternal('https://dirask.com')); // false30
console.log(isExternal('https://dirask.com/snippets')); // false31
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console.log(isExternal('https://google.com')); // true33
console.log(isExternal('https://google.com/about')); // trueNote: the solution uses
location.originproperty that is available in web browsers only.
Note: in the above example, URLs are tested as external, according to current origin - Dirask origin.
URL can be external according to indicated origin.
It means:
- for https://google.com origin, all Dirask links will be external,
- for https://dirask.com origin, all Google links will be external,
Practical example:
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const googleOrigin = 'https://google.com';2
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console.log(isExternal('https://dirask.com', googleOrigin)); // true4
console.log(isExternal('https://dirask.com/snippets', googleOrigin)); // true5
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const diraskOrigin = 'https://dirask.com';8
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console.log(isExternal('https://google.com', diraskOrigin)); // true10
console.log(isExternal('https://google.com/about', diraskOrigin)); // true
