HTML and CSS Reference
In-Depth Information
The JavaScript eval() function evaluates and/or executes a string of JavaScript
code. First, eval() determines if the argument is a valid string, i.e., the JSON string
that was returned from the server. Then eval() parses the string. The string re-
turned from the eval() is a JavaScript object.
The variable details will hold the properties and values of the JavaScript object.
JavaScript's special f or/in loop provides a mechanism for stepping through all the
properties of an object. It iterates through the carObject , retrieving both properties
and values to be placed in the div container on line 8.
If the property is “owner”, it has a nested set of key/value pairs as shown here:
{ "make":"Honda Civic",
"name":"Henry Lee",
"cellphone": "222-222-2222",
"address":{"street": "10 Main",
"city": "San Francisco",
"state": "CA"
"dealer": "SF Honda"
The special for/in loop iterates through the object's properties. To get the value of
a property, the property is placed between square brackets (associative array) pre-
ceded by the name of the object. In a nested object, the dot syntax is used to get
to the nested property as: carObject[“owner”].name or carObject[“owner”].ad-
Each time through the loop, a property and its value will be added to the details
variable until all properties/values have been collected. In this example, the ad-
dress was not included, only to keep the program size smaller.
The DOM's innerHTML property will be assigned all of the details collected for the
carObject and placed in the div container on line 8, Figure 18.20.
When the user clicks this button, the makeRequest() function will be called to cre-
ate an Ajax request object and handle the JSON data (see page 840).
This is the div container where the display data will be placed. The results is
shown in Figure 18.20.
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