试试这个：

function generatePDF(){
      
    var element = document.getElementById('purchase-paper');
    var opt = {
        margin: 1,
        filename: 'test.pdf',
        image: {type:'jpeg',quality:0.98},
        jsPDF: {unit:'in',format:'letter',orientation:'portrait'},
        pageBreakBefore: function(currentNode, followingNodesOnPage, nodesOnNextPage, previousNodesOnPage) {
            if (currentNode.id === 'purchase-paper') {
                return true;
            }
            return false;
        }
    };
    html2pdf().set(opt).from(element).save();

}