💾elem.position()

element's top-left corner coordinates relative to the document page.

🔰 JS ⟩ browser ⟩ DOM ⟩ types ⟩ Element ⟩ methods ⟩ .position()

box models

當視窗捲動時：

Element 的 .boundingBox 的位置座標 (.x, .y) 會變
viewport 的位置座標 (.scrollX, .scrollY) 會變

但 Element 相對於 document 的座標 (elem.page) 不會變。

// 🔸 elem.position()
Element.prototype.position = function(coordSystem='document'){
    // viewport to element = (x, y)
    const {x, y} = this.getBoundingClientRect();
    switch(coordSystem){
        // relative to "viewport"
        case 'viewport': return vec(x, y);
        // relative to "document"
        // document to viewport = (scrollX, scrollY)
        default: return vec(scrollX + x, scrollY + y);
    }
};

💈範例：

// elements
const doc = document.documentElement;    // <html> element
const info = $('#scrollInfo');
const span1 = $('#span1');
const coords = $('#pageCoords');

// scroll handler
window.onscroll = (event) => {
    info.innerText = `viewport in page: ${viewport.positionInDocument}`;
    coords.innerHTML = `
        span in page: ${span1.position()}<br>
        span in viewport: ${span1.position('viewport')}
    `;
};

Previouselem.showDataAttr()NextHTMLElement

Last updated 1 year ago