給予寬度，算出圖片等比例高度

Here’s a simple JavaScript example to calculate the proportional height of an image when you set a fixed width:

function calculateProportionalHeight(originalWidth, originalHeight, newWidth) {
  const newHeight = (originalHeight * newWidth) / originalWidth;
  return newHeight;
}

// Example usage:
const originalWidth = 800;
const originalHeight = 600;
const newWidth = 400;

const newHeight = calculateProportionalHeight(originalWidth, originalHeight, newWidth);
console.log(`The proportional height for the new width is: ${newHeight}px`);

Explanation

• The calculateProportionalHeight function takes the original width, original height, and the new width as arguments.
• It calculates the new height using the formula we discussed and returns it.

In this example, if the original dimensions are 800×600, and you set a new width of 400, the function will calculate the new height that maintains the image’s aspect ratio.

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