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[英]How do I check if a particular object exist or not in a JavaScript array of objects?
[英]How can I check index in object array exist or no in javascript?
我的JavaScript代码是这样的:
<script type="text/javascript">
var team = [{id:"1", name:"chelsea"}, {id:"3", name:"mu"}, {id:"5", name:"arsenal"}];
for(var i = 0; i < 5; i++) {
if(team[i].id || typeof team[i].id !== 'undefined' || team[i].id !== null) {
console.log(team[i].id)
}
else {
console.log(i+1)
}
}
</script>
如果代码运行,则在控制台上存在如下错误:
未捕获的TypeError:无法读取未定义的属性“ id”
而如果变量不存在,我有添加条件
我该如何解决?
据我了解,当您在评论输出1,2,3,4,5
说您需要缺少ID时-在您的情况下,有2,4
var team = [{id:"1", name:"chelsea"}, {id:"3", name:"mu"}, {id:"5", name:"arsenal"}]; var empty_ids = 0; for(var i = 0; i < 5; i++) { if(team[i] && typeof team[i] !== 'undefined' && team[i] !== null) { if(parseInt(team[i].id) !== i + 1){ // check if id on the array not equal the i + 1 from the loop for( var k= 1 ; k < parseInt(team[i].id) - empty_ids ; k++){ console.log(empty_ids + k +" missing"); } console.log(team[i].id); }else{ console.log(team[i].id); } empty_ids = parseInt(team[i].id); }else{ if(empty_ids <= i){ console.log(empty_ids + 1 + " undefined team[i]"); empty_ids = empty_ids + 1; } } }
注意 :即使更改团队数组,此代码也将起作用
var team = [{id:"1", name:"chelsea"}, {id:"5", name:"arsenal"}];
//or
var team = [{id:"1", name:"chelsea"}, {id:"3", name:"mu"}, {id:"4", name:"arsenal"}];
//or
var team = [{id:"1", name:"chelsea"}, {id:"4", name:"arsenal"}];
因此,请尝试将var team =
更改为建议值..我添加了一个missing
和undefined
以使您注意到console.log
来源
很少的观察,
这是修改后的代码,
<script type="text/javascript">
var team = [{id:"1", name:"chelsea"}, {id:"3", name:"mu"}, {id:"5", name:"arsenal"}];
for(var i = 0; i < team.length; i++) {
if(team[i].id || typeof team[i].id !== 'undefined' || team[i].id !== null) {
console.log(team[i].id)
}
else {
console.log('team id not found for index ' + i);
}
}
</script>
主要问题是您正在检查对象的属性,在本例中为team [i],可能未定义。
例如,如果您使用console.log(team [4]),它将指向未定义,因为团队中只有3个对象。 检查未定义的属性将导致错误。
var arr = [1,2,3] // this will be undefined var element = arr[4] console.log(element.toString)
因此,您还应该检查team [i]是否未定义。 您的代码应类似于以下代码。 我假设您要打印1、2、3、4、5。
var team = [{id:"1", name:"chelsea"}, {id:"3", name:"mu"}, {id:"5", name:"arsenal"}]; for(var i = 0; i < 5; i++) { // check if team[i] is not undefined using (team[i] !== undefined) if((team[i] !== undefined) && ( team[i].id || typeof team[i].id !== 'undefined' || team[i].id !== null)) { var currentId = team[i].id > i + 1 ? i + 1 : team[i].id; console.log(currentId) } else { console.log(i + 1); } }
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