这个变量怎么还是NULL

Question

我正在编写一个 CasperJS 脚本来自动执行搜索表单并捕获后续页面。但是，搜索表单首先进入加载启动页面，直到数据到达。所以我添加了 waitForSelector 函数，它似乎适用于我的某些页面，但其他 return 变量 name 为 NULL。如果该元素确实 "waiting" 在 DOM 上，那怎么可能？

casper.each(searchPages,function(casper,index){
    var currentTime = new Date();
    var month = currentTime.getMonth() + 2;
    var day = currentTime.getDate();
    var year = currentTime.getFullYear();
    var dateStart = month + "/" + day + "/" + year;
    month = currentTime.getMonth() + 3;
    var dateEnd = month + "/" + day + "/" + year;

    casper.thenOpen(url,function(){
        var myfile = "data-"+year + "-" + month + "-" + day+".html";
        this.evaluate(function(j) {
            document.querySelector('select[name="searchParameters.localeId"]').selectedIndex = j;
        },index);
        this.evaluate(function(start) {
            $("#leaveDate").val(start);
        },dateStart);
        this.evaluate(function(end) {
            $("#returnDate").val(end);
        },dateEnd);
        this.evaluate(function() {
            $("#OSB_btn").click();
        });

        this.waitForSelector('#destinationForPackage', function() {
            var name = casper.evaluate(function() {
                return $("#destinationForPackage option[value='" + $("#destinationForPackage").val() + "']").text()
            });
            if (name != "Going To"){
                if (name == null){
                    console.log("it's null");
                }else{
                    name = name.replace("/","_");
                    casper.capture('Captures/Searches/search_' + name + '.jpg');
                    console.log("Capturing search_" + name);
                }
            }
        },function(){
            console.log("Search page timed-out.");  
        },20000);
    });
});

Answer 1

如果元素仍然不可用，我可以通过创建递归函数来解决这个问题。现在我遇到了内存问题，这里有新问题 => CasperJS running out of memory

casper.each(searchPages,function(casper,index){
    loadSearch(casper,index);
});


function loadSearch(casper,index){
    var currentTime = new Date();
    var month = currentTime.getMonth() + 2;
    var day = currentTime.getDate();
    var year = currentTime.getFullYear();
    var dateStart = month + "/" + day + "/" + year;
    month = currentTime.getMonth() + 3;
    var dateEnd = month + "/" + day + "/" + year;

    casper.thenOpen(url,function(){
        var myfile = "data-"+year + "-" + month + "-" + day+".html";
        this.evaluate(function(j) {
            document.querySelector('select[name="searchParameters.localeId"]').selectedIndex = j;
        },index);
        this.evaluate(function(start) {
            $("#leaveDate").val(start);
        },dateStart);
        this.evaluate(function(end) {
            $("#returnDate").val(end);
        },dateEnd);
        this.evaluate(function() {
            $("#OSB_btn").click();
        });

        this.waitForSelector('#destinationForPackage', function() {
            if (this.exists('#destinationForPackage')){
                var name = casper.evaluate(function() {
                    return $("#destinationForPackage option[value='" + $("#destinationForPackage").val() + "']").text()
                });
                if (name != "Going To"){
                    if (name == null){
                        console.log("it's null");
                    }else{
                        name = name.replace("/","_");
                        casper.capture('Captures/Searches/search_' + name + '.jpg');
                        console.log("Capturing search_" + name);
                    }
                }
            }else{
                console.log("Still doesn't exist...retry");
                loadSearch(casper,index);
            }

        },function(){
            console.log("Search page timed-out.");  
        },20000);
    });
}

这个变量怎么还是NULL

How is this variable still NULL

javascript

phantomjs

casperjs