replace(/(.*)\/(.*)/, "newPath/$2"); <img id="mainImage" src="default.jpg" alt="Main image"> <a href="#" onclick="document.getElementById('mainImage').src='large_image.jpg'; return false;"> <img src="thumbnail.jpg" </a> <img src="path/to/image.jpg" onclick="window.location.href='> <img src="path/to/image.jpg" onclick="this.src=location.href='> <img src="path/to/image20-10.jpg" onclick="this.src = this.src.replace(/\-(\d+)/g, (match, p1) => { return parseInt(p1) + 1; });"> let newStr = str.replace(/\-(\d+)/g, (match, p1) => { return parseInt(p1) + 1; });