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JavaScript - rotate localized vector 2D to left direction (counterclockwise direction)
7 points
In this short article, we would like to show how to rotate any localized vector 2D to the left side (90 degrees) using Javascript.
Quick solution:
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function rotateLeft(vector) {2
var a = vector.a;3
var b = vector.b;4
return {5
a: { x: -a.y, y: a.x }, // check: https://dirask.com/posts/1GoW616
b: { x: -b.y, y: b.x }7
};8
}9
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var vector1 = {a: {x: 1, y: 2}, b: {x: 2, y: 4}}; // vector [A1, B1] = ( 1, 2) -> ( 2, 4)11
var vector2 = rotateLeft(vector1); // vector [A2, B2] = (-2, 1) -> (-4, 2)Rotation preview:
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function rotateLeft(vector) {2
var a = vector.a;3
var b = vector.b;4
return {5
a: { x: -a.y, y: a.x }, // check: https://dirask.com/posts/1GoW616
b: { x: -b.y, y: b.x }7
};8
}9
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// Helper methods:12
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function printPoint(point) {14
return '(' + point.x + ', ' + point.y + ')';15
}16
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function printVector(name, vector) {18
console.log(name + ': ' + printPoint(vector.a) + ' -> ' + printPoint(vector.b));19
}20
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// Usage example:23
// direction:24
var vector1 = { // ↑25
a: {x: 0, y: 1}, // a = beginning point26
b: {x: 0, y: 2} // b = ending point (arrow/head)27
}; 28
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var vector2 = rotateLeft(vector1); // ←30
var vector3 = rotateLeft(vector2); // ↓31
var vector4 = rotateLeft(vector3); // →32
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printVector('vector1', vector1); // ( 0, 1) -> ( 0, 2) ↑34
printVector('vector2', vector2); // (-1, 0) -> (-2, 0) ←35
printVector('vector3', vector3); // ( 0, -1) -> ( 0, -2) ↓36
printVector('vector4', vector4); // ( 1, 0) -> ( 2, 0) →