Question

不确定确切要问什么。但是，我的代码如下。我想做的是使用listPlanets（）;在if语句中返回用户键入到提示中的数组项。

任何帮助都会很好。

var planets = [
    {planet: 'Mercury', position: '1', orbit_time: '0.24', nat_satellites: '0'},
    {planet: 'Venus', position: '2', orbit_time: '0.62', nat_satellites: '0'},
    {planet: 'Earth', position: '3', orbit_time: '1', nat_satellites: '1'},
    {planet: 'Mars', position: '4', orbit_time: '1.88', nat_satellites: '2'},
    {planet: 'Jupiter', position: '5', orbit_time: '11.86', nat_satellites: '67'},
    {planet: 'Saturn', position: '6', orbit_time: '29.46', nat_satellites: '62'},
    {planet: 'Uranus', position: '7', orbit_time: '84.32', nat_satellites: '27'},
    {planet: 'Neptune', position: '8', orbit_time: '164.79', nat_satellites: '14'}
];

var listPlanets = function () {
    for (var i = 0; i < planets.length; i++) {
        document.write(planets[i].planet + ' is planet #' + planets[i].position + 
            ' from the Sun. Time to complete its orbit is ' + planets[i].orbit_time + ' earth year(s). It has ' + planets[i].nat_satellites + ' natural satellite(s).<br>' );
    }
}

// listPlanets();

var num = window.prompt("Please enter a number between 1 and 8");

if (1 <= num && num <= 8) {
    listPlanets();
} else {
    alert("The value you entered is not within range. Please reload the page and enter a value thatis within 1 and 8, inclusive."); 
    window.location.reload();
}

Answer 1

@dgeare的答案之所以有效，是因为数组索引与位置属性值匹配。您还可以通过在if函数中添加一个简单的listPlanets语句来完成此操作，以检查该函数的参数和position属性是否匹配。

var planets = [
    {planet: 'Mercury', position: '1', orbit_time: '0.24', nat_satellites: '0'},
    {planet: 'Venus', position: '2', orbit_time: '0.62', nat_satellites: '0'},
    {planet: 'Earth', position: '3', orbit_time: '1', nat_satellites: '1'},
    {planet: 'Mars', position: '4', orbit_time: '1.88', nat_satellites: '2'},
    {planet: 'Jupiter', position: '5', orbit_time: '11.86', nat_satellites: '67'},
    {planet: 'Saturn', position: '6', orbit_time: '29.46', nat_satellites: '62'},
    {planet: 'Uranus', position: '7', orbit_time: '84.32', nat_satellites: '27'},
    {planet: 'Neptune', position: '8', orbit_time: '164.79', nat_satellites: '14'}
];

var listPlanets = function (userInput) {
   for (var i = 0; i < planets.length; i++) {
       if (planets[i].position == userInput) {
          document.write(planets[i].planet + ' is planet #' + planets[i].position + 
              ' from the Sun. Time to complete its orbit is ' + planets[i].orbit_time + ' earth year(s). It has ' + planets[i].nat_satellites + ' natural satellite(s).<br>' ); 
       }
   }
}

// listPlanets();

var num = window.prompt("Please enter a number between 1 and 8");

if (1 <= num && num <= 8) {
    listPlanets(num);
} else {
    alert("The value you entered is not within range. Please reload the page and enter a value thatis within 1 and 8, inclusive."); 
    window.location.reload();
}

Answer 2

我认为您的意思是将输入的值作为参数传递给listPlanets函数？

var planets = [
    {planet: 'Mercury', position: '1', orbit_time: '0.24', nat_satellites: '0'},
    {planet: 'Venus', position: '2', orbit_time: '0.62', nat_satellites: '0'},
    {planet: 'Earth', position: '3', orbit_time: '1', nat_satellites: '1'},
    {planet: 'Mars', position: '4', orbit_time: '1.88', nat_satellites: '2'},
    {planet: 'Jupiter', position: '5', orbit_time: '11.86', nat_satellites: '67'},
    {planet: 'Saturn', position: '6', orbit_time: '29.46', nat_satellites: '62'},
    {planet: 'Uranus', position: '7', orbit_time: '84.32', nat_satellites: '27'},
    {planet: 'Neptune', position: '8', orbit_time: '164.79', nat_satellites: '14'}
];

var listPlanets = function (i) { //i is a parameter that will be passed into the function at the time it is called
   i -= 1;//the user entered a value between 1 and 8, but our array indexes are from 0 - 7. decrease input by one
   document.write(planets[i].planet + ' is planet #' + planets[i].position + 
            ' from the Sun. Time to complete its orbit is ' + planets[i].orbit_time + ' earth year(s). It has ' + planets[i].nat_satellites + ' natural satellite(s).<br>' );
    
}

// listPlanets();

var num = window.prompt("Please enter a number between 1 and 8");

if (1 <= num && num <= 8) {
    listPlanets(num); //pass num into listPlanets function as argument
} else {
    alert("The value you entered is not within range. Please reload the page and enter a value thatis within 1 and 8, inclusive."); 
    window.location.reload();
}

在上面的代码中，我删除了循环，因为我们已经知道用户的选择。无需执行遍历数组中每个项目的工作，因为我们可以直接访问该项目。由于数组在JavaScript中是基于0的，因此我们需要通过将用户输入减少1来解决这个问题。

正如一些评论所指出的那样，您可能更希望将数据反映到DOM而不是document.write，这会覆盖现有页面，通常被认为是不好的做法。如果您要在DOM中执行此操作，则它看起来可能像这样：

var planets = [
    {planet: 'Mercury', position: '1', orbit_time: '0.24', nat_satellites: '0'},
    {planet: 'Venus', position: '2', orbit_time: '0.62', nat_satellites: '0'},
    {planet: 'Earth', position: '3', orbit_time: '1', nat_satellites: '1'},
    {planet: 'Mars', position: '4', orbit_time: '1.88', nat_satellites: '2'},
    {planet: 'Jupiter', position: '5', orbit_time: '11.86', nat_satellites: '67'},
    {planet: 'Saturn', position: '6', orbit_time: '29.46', nat_satellites: '62'},
    {planet: 'Uranus', position: '7', orbit_time: '84.32', nat_satellites: '27'},
    {planet: 'Neptune', position: '8', orbit_time: '164.79', nat_satellites: '14'}
];

var listPlanets = function (i) {
   i -= 1;
   document.getElementById('planet_name').innerHTML = planets[i].planet;
   document.getElementById('planet_info').innerHTML = planets[i].planet + ' is planet #' + planets[i].position + 
            ' from the Sun. Time to complete its orbit is ' + planets[i].orbit_time + ' earth year(s). It has ' + planets[i].nat_satellites + ' natural satellite(s).<br>';
    
}

// listPlanets();


document.getElementById('info_button').addEventListener('click', function(evt){
  var num = document.getElementById('planet_input').value;
  if (1 <= num && num <= 8) {
      listPlanets(num);
  } else {
      alert("The value you entered is not within range. Please reload the page and enter a value thatis within 1 and 8, inclusive."); 

  }
});

Pick a planet between 1 and 8 <input id='planet_input' type='number' /><button id='info_button'>View Info</button>
<h1 id='planet_name'></h1>
<h3 id='planet_info'></h3>

Answer 3

您应该将在提示中输入的索引作为函数参数传递，并使用它来获取数组中的给定项：

var planets = [...];

var listPlanets = function (num) {
    var planet = planets[num];

    var thingToWrite = planet.planet + ' is planet #' + planet.position + ' from the Sun. Time to complete its orbit is ' + planet.orbit_time ' +  earth year(s). It has ' + planet.nat_satellites + ' natural satellite(s).<br>'

    document.write(thingToWrite);      
}

var num = window.prompt("Please enter a number between 1 and 8");

if (1 <= num && num <= 8) {
    listPlanets(num);
} else {
    alert("The value you entered is not within range. Please reload the page and enter a value thatis within 1 and 8, inclusive."); 
    window.location.reload();
}

最好的问候，伊沃

您可以从函数中选择数组中的特定位置吗？

3 个答案: