javascript - 在 json 中使用游标时无法读取未定义的属性 'length'

Question

我有一个以 json 格式返回数据的 php 脚本:

[{"text_content":"gdgdsg","text_duration":"15"},{"text_content":"gdgdsg","text_duration":"15"},{"text_content":"gdgdsg","text_duration":"15"},

等]

我有一个 jquery 脚本来解析输入并在屏幕上显示文本:

var results;
var cursor = 0;

function myFunction () {
    $.getJSON('list2.php', function(json) {
        results = json.result;
        cursor = 0;

        // Now start printing
        printNext();
    });
}

function printNext(){
    if(cursor == results.length){
        // Reset the cursor back to the beginning.
        cursor = 0;
    }

    // Print the key1 in the div.
    $('#mydiv').hide('fast', function(){ $('#mydiv').html(results[cursor].text_content); $('#mydiv').show('fast'); });

    // Set a delay for the current item to stay
    // Delay is key2 * 1000 seconds
    setTimeout(function(){
        printNext();
    }, results[cursor].text_duration * 1000);

    // Advance the cursor.
    cursor++;
}

但是当我运行它时出现以下错误:

Uncaught TypeError: Cannot read property 'length' of undefined

在这一行中:

if(cursor == results.length){

这里可能出了什么问题？

编辑:

返回数据到json的php代码是:

if ($result = $mysqli->query("SELECT text_content, text_duration from user_text")) {

while($row = $result->fetch_array(MYSQL_ASSOC)) {
            $myArray[] = $row;
    }
    echo json_encode($myArray);
}

Answer 1

getJSON回调函数返回json数据。

var results= [];
    var cursor = 0;

function myFunction () {
    $.getJSON('list2.php', function(json) {
        results = json;
        cursor = 0;

        // Now start printing
        printNext();
    });
}

function printNext(){
    if(cursor == results.length){
        // Reset the cursor back to the beginning.
        cursor = 0;
    }

    // Print the key1 in the div.
    $('#mydiv').hide('fast', function(){ $('#mydiv').html(results[cursor].text_content); $('#mydiv').show('fast'); });

    // Set a delay for the current item to stay
    // Delay is key2 * 1000 seconds
    setTimeout(function(){
        printNext();
    }, results[cursor].text_duration * 1000);

    // Advance the cursor.
    cursor++;
}