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<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>Title</title> </head> <body> <div id="div1" style=" 100px; height: 100px; padding:10px;border: 1px solid red;"></div> <script> window.onload = function () { var oDiv = document.getElementById('div1') console.log(oDiv.style.width) //100 样式宽 console.log(oDiv.clientWidth) //120 可视区宽 = 样式宽 + padding console.log(oDiv.offsetWidth) //122 占位宽 = 可视区宽 + border } </script> </body> </html>