我使用以下javascript函数的问题是,它返回的字符串值为mostpopular,因为“不是程序员”,所以虽然它正在执行我的console.log命令所在的正确操作,但它返回最流行尚未修改的变量。如果我修改顶部的变量为什么不返回修改...它几乎像javascript生成一个实例,它只适用于测试函数的本地设置(如果我放置console.log语句,它打印出来正确的数据)。这是为什么?
var mostPopular = "not a programmer";
var totalResults = 0;
function myfunction() {
var listOfLanguages = ["Java", "C", "C++", "PHP", "C#", "Visual Basic", "Python", "Objective-C", "Perl", "Javascript", "Ruby"];
for (var i = 0; i < listOfLanguages.length - 1; i++) {
chrome.history.search({
text: listOfLanguages[i],
maxResults: 100
}, function (search_results) {
var countOfResults = search_results.length;
var langOfResults = listOfLanguages[i - 1];
test(countOfResults, langOfResults);
});
}
console.log(mostPopular);
}
function test(count, lang) {
if (count > totalResults) {
totalResults = count;
mostPopular = lang;
}
}
window.onload = myfunction;
答案 0 :(得分:2)
如上所述,历史搜索是异步的,因此在完成时需要执行回调
它的工作原理如下:
var mostPopular = "not a programmer";
var totalResults = 0;
function myfunction() {
var listOfLanguages = ["Java", "C", "C++", "PHP", "C#", "Visual Basic", "Python", "Objective-C", "Perl", "Javascript", "Ruby"];
for (var i = 0; i < listOfLanguages.length - 1; i++) {
chrome.history.search({
text: listOfLanguages[i],
maxResults: 100
}, function (search_results) {
var countOfResults = search_results.length;
var langOfResults = listOfLanguages[i - 1];
test(countOfResults, langOfResults);
console.log(mostPopular);
// The Code will execute whenever the history search results are returned
});
}
// Any code here will be exceuted irrespective of the history search completed or not
}
function test(count, lang) {
if (count > totalResults) {
totalResults = count;
mostPopular = lang;
}
}
window.onload = myfunction;