JavaScript

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How to pass an ASP.net variable to a JavaScript function?

Passing an ASP.NET variable to a JavaScript function is quite easy. Regarding the type of variable, one may consider the following cases:

1. A single variable

A single variable is the simplest case. The only requirement is that the variable must be visible to the JavaScript code and thus, we declare it other than private.

protected int test = 10;

Then, on the ASP.NET page,

<script>
  var t = "<%= test%>";
</script>

2. An array

An array is a non-primitive data type. For passing it to a JavaScript variable, we first need to serialize it. Therefore, we declare a serializer.

protected int[] test = new int[3];

protected System.Web.Script.Serialization.JavaScriptSerializer serializer = new System.Web.Script.Serialization.JavaScriptSerializer();

Then, in the ASP.NET page, we call the serializer before we pass the variable, like this:

<script>
    var t = "<%=serializer.Serialize(test) %>";
</script>

By default, the maximum length of the JSON string produced by the serializer is 2,097,152 characters. One can increase this length to its maximum value as follows:

jsSerializer.MaxJsonLength = 2147483647;

where the variable MaxJsonLength is of int32 type and 2147483647 is the maximum signed positive int32 number.