如何在javascript中获取json编码数组的长度？
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/19516871/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
how to get length of json encoded array in javascript?
提问by DS9
I have a json encoded array like this:
我有一个像这样的 json 编码数组：
{
"ar0":"{\"start\":{\"lat\":22.9939202,\"lng\":72.50009499999999},\"end\":{\"lat\":23.0394491,\"lng\":72.51248850000002},\"waypoints\":[[23.0316834,72.4779436]]}",
"ar1":"{\"start\":{\"lat\":22.9999061,\"lng\":72.65318300000001},\"end\":{\"lat\":23.0420584,\"lng\":72.67145549999998},\"waypoints\":[[23.02237,72.6500747]]}",
"ar2":"{\"start\":{\"lat\":23.0394491,\"lng\":72.51248850000002},\"end\":{\"lat\":22.9999061,\"lng\":72.65318300000001},\"waypoints\":[[23.0016629,72.58898380000005]]}"
}
my quetion is :
我的问题是：
(1) How to find length of this array? //here it is 3
(1) 如何求这个数组的长度？ //here it is 3
(2) How to use it's value?//for example:for as0 the value is {\"start\":{\"lat\":22.9939202,\"lng\":72.50009499999999},\"end\":{\"lat\":23.0394491,\"lng\":72.51248850000002},\"waypoints\":[[23.0316834,72.4779436]]}
(2) 如何使用它的价值？//for example:for as0 the value is {\"start\":{\"lat\":22.9939202,\"lng\":72.50009499999999},\"end\":{\"lat\":23.0394491,\"lng\":72.51248850000002},\"waypoints\":[[23.0316834,72.4779436]]}
javascript code where i use upper things :
javascript code where i use upper things :
function setroute(os)
{
var wp = [];
for(var i=0;i<os.waypoints.length;i++)
wp[i] = {'location': new google.maps.LatLng(os.waypoints[i][0], os.waypoints[i][1]),'stopover':false }
ser.route({'origin':new google.maps.LatLng(os.start.lat,os.start.lng),
'destination':new google.maps.LatLng(os.end.lat,os.end.lng),
'waypoints': wp,
'travelMode': google.maps.DirectionsTravelMode.DRIVING},function(res,sts) {
if(sts=='OK')ren.setDirections(res);
})
}
function fetchdata()
{
var jax = window.XMLHttpRequest ? new XMLHttpRequest() : new ActiveXObject('Microsoft.XMLHTTP');
jax.open('POST','process.php');
jax.setRequestHeader('Content-Type','application/x-www-form-urlencoded');
jax.send('command=fetch')
jax.onreadystatechange = function(){ if(jax.readyState==4) {
alert(JSON.parse(jax.responseText).ar0);
try {
console.log(jax.responseText);
//it is not work
for(var i=0;i<JSON.parse(jax.responseText).length;i++)
{
setroute( eval('(' + jax.responseText + ')') );
}
}
catch(e){ alert(e); }
}}
}
回答by Pith
Your JSON is not an array, but an object. If you want it to be an array, it should be something like this:
您的 JSON 不是数组，而是一个对象。如果你希望它是一个数组，它应该是这样的：
[
"{\"start\":{\"lat\":22.9939202,\"lng\":72.50009499999999},\"end\":{\"lat\":23.0394491,\"lng\":72.51248850000002},\"waypoints\":[[23.0316834,72.4779436]]}",
"{\"start\":{\"lat\":22.9999061,\"lng\":72.65318300000001},\"end\":{\"lat\":23.0420584,\"lng\":72.67145549999998},\"waypoints\":[[23.02237,72.6500747]]}",
"{\"start\":{\"lat\":23.0394491,\"lng\":72.51248850000002},\"end\":{\"lat\":22.9999061,\"lng\":72.65318300000001},\"waypoints\":[[23.0016629,72.58898380000005]]}"
]
Then, you can get a javascript array as follows:
然后，您可以获得一个 javascript 数组，如下所示：
var array = JSON.parse(jax.responseText);
And access values as follows:
并访问值如下：
array[0]
array.length
EDIT:In order to have a real JSON array with the PHP json_encodemethod, see this related question.
编辑：为了使用 PHPjson_encode方法获得真正的 JSON 数组，请参阅此相关问题。
With this modification you will be able to use all the possibilities of JS array without workaround.
通过此修改，您将能够使用 JS 数组的所有可能性而无需解决方法。
回答by Halcyon
Objects in JavaScript don't have a .lengthproperty like Arrays do.
JavaScript 中的对象没有.length像数组那样的属性。
In ES5 you can do: Object.keys({}).length; // 0
在 ES5 中，您可以执行以下操作： Object.keys({}).length; // 0
The other solution would be to loop over all the properties of your object with a for .. inloop and count.
另一种解决方案是使用for .. in循环和计数循环遍历对象的所有属性。
回答by Hasib Hasan Arnab
You can use the following code. It will produce your desired output 3
您可以使用以下代码。它将产生您想要的输出 3
var test = {
"ar0":"{\"start\":{\"lat\":22.9939202,\"lng\":72.50009499999999},\"end\":{\"lat\":23.0394491,\"lng\":72.51248850000002},\"waypoints\":[[23.0316834,72.4779436]]}",
"ar1":"{\"start\":{\"lat\":22.9999061,\"lng\":72.65318300000001},\"end\":{\"lat\":23.0420584,\"lng\":72.67145549999998},\"waypoints\":[[23.02237,72.6500747]]}",
"ar2":"{\"start\":{\"lat\":23.0394491,\"lng\":72.51248850000002},\"end\":{\"lat\":22.9999061,\"lng\":72.65318300000001},\"waypoints\":[[23.0016629,72.58898380000005]]}"
}
var getLength = function(obj) {
var i = 0, key;
for (key in obj) {
if (obj.hasOwnProperty(key)){
i++;
}
}
return i;
};
console.log(getLength(test));
回答by Kippie
For your first question, you should use Object.keys(item).length
对于您的第一个问题，您应该使用 Object.keys(item).length
To get the values of your object, you should iterate over it with a forloop:
要获取对象的值，您应该使用循环对其进行迭代for：
for(var key in item)
{
var val = item[key];
}
for(var key in item)
{
var val = item[key];
}
回答by bhb
var count = 0;
Object.keys(json).forEach(function (key) {
count++;
alert(json[key].start.lat);
});
alert(count);
Using jQuery
使用 jQuery
$(json).each(function() { count++; alert(this.start.lat); });
alert(count);
