我正在使用Titanium,我的代码看起来是这样的:

var currentData = new Array();
if(currentData[index]!==""||currentData[index]!==null||currentData[index]!=='null')
{
    Ti.API.info("is exists  " + currentData[index]);
    return true;
}
else
{   
    return false;
}

我传递一个索引到currentData数组。使用上面的代码,我仍然无法检测到不存在的索引。


当前回答

var demoArray = ['A','B','C','D'];
var ArrayIndexValue = 2;
if(ArrayIndexValue in demoArray){
   //Array index exists
}else{
   //Array Index does not Exists
}

其他回答

考虑数组a:

var a ={'name1':1, 'name2':2}

如果你想检查'name1'是否存在于a中,只需用in测试它:

if('name1' in a){
console.log('name1 exists in a')
}else
console.log('name1 is not in a')
var myArray = ["Banana", "Orange", "Apple", "Mango"];

if (myArray.indexOf(searchTerm) === -1) {
  console.log("element doesn't exist");
}
else {
  console.log("element found");
}

这也很好,使用===对undefined进行类型测试。

if (array[index] === undefined){ return } // True

测试:

const fruits =["香蕉","橘子","苹果","芒果"]; if (fruit ["Cherry"] === undefined){ console.log("There 't any cherry in the fruits basket:(") }

或类似的:

const fruits =["香蕉","橘子","苹果","芒果"]; 如果(!水果(“樱桃”)){ console.log("There 't any cherry in the fruits basket:(") } //没有错误: 如果(水果(“樱桃”)){ console.log(“里面有樱桃!”) }

(typeof files[1] === undefined)?
            this.props.upload({file: files}):
            this.props.postMultipleUpload({file: files widgetIndex: 0, id})

使用typeof检查数组中的第二项是否为undefined,并检查是否为undefined

你可以简单地使用这个:

var tmp = ['a', 'b'];
index = 3 ;
if( tmp[index]){
    console.log(tmp[index] + '\n');
}else{
    console.log(' does not exist');
}