EN
JavaScript - remove duplicated lines
8 points
In this short article, we would like to show how to remove duplicated lines from some text using JavaScript.
Quick solution:
xxxxxxxxxx1
const newLineExpression = /\r\n|\n\r|\n|\r/g;2
3
const removeDuplicatedLines = (text) => {4
let result = '';5
const blocker = {}; // prevents lines dupplication6
const lines = text.split(newLineExpression);7
for (const line of lines) {8
if (blocker.hasOwnProperty(line)) {9
continue;10
}11
blocker[line] = true;12
result += line + '\n';13
}14
return result;15
};16
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// Usage example:18
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const text = `a20
b21
b22
a23
a24
c25
c`;26
27
console.log(removeDuplicatedLines(text)); // a28
// b29
// cThis approach uses a functional programming pattern.
xxxxxxxxxx1
const newLineExpression = /\r\n|\n\r|\n|\r/g;2
3
const removeDuplicatedLines = (text) => {4
return text.split(newLineExpression)5
.filter((item, index, array) => array.indexOf(item) === index)6
.join('\n');7
};8
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// Usage example:10
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const text = `a12
b13
b14
a15
a16
c17
c`;18
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console.log(removeDuplicatedLines(text)); // a20
// b21
// cThis approach was created to show that it is possible to get the same effect with reduce() method.
xxxxxxxxxx1
const newLineExpression = /\r\n|\n\r|\n|\r/g;2
3
const removeDuplicatedLines = (text) => {4
const blocker = {}; // prevents lines dupplication5
return text.split(newLineExpression)6
.reduce((result, line) => {7
if (blocker.hasOwnProperty(line)) {8
return result;9
}10
blocker[line] = true;11
return result + line + '\n';12
}, '');13
};14
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// Usage example:16
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const text = `a18
b19
b20
a21
a22
c23
c`;24
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console.log(removeDuplicatedLines(text)); // a26
// b27
// c