document.execCommand("copy")

documentCopy.js

n.copy = function(e, n, o) {
        var c = d('<span class="my-gallery-src-copy-hidden">' + e + "</span>")
          , s = d("body");
        s.append(c);
        var a = document.createRange();
        a.selectNode(c.get(0));
        var i = window.getSelection();
        i.removeAllRanges(),
        i.addRange(a);
        var t = document.execCommand("copy");
        c.remove(),
        n && n(t),
        o && (s.find(".kb-g-copy-success-info").remove(),
        clearTimeout(p),
        s.append(d('<span class="kb-g-copy-success-info">\u590d\u5236\u6210\u529f</span>').css({
            position: "fixed",
            top: o.y - 50,
            left: o.x - 10,
            "z-index": 1e6
        })),
        p = setTimeout(function() {
            s.find(".kb-g-copy-success-info").remove()
        }, 1e3))
    }