Analysis of C/c++,java,php,javascript,json array, object assignment when the last element can be followed by commas _javascript tips

1 c,c++,java,php can tolerate the comma at the end.

When an array is assigned to a C,c++,java, the comma at the end of the last element is optional. The following two lines of code are equivalent to these languages.

int a[] = {1,2,3}; /* correct
/int a[] = {1,2,3,}//* correct * *

PHP also inherits the features of C, and the following two lines of code are equivalent.

$a = array (1,2,3); /* Correct
/$a = array (1,2,3,);/* Correct */

2 JavaScript sees the end comma as a syntax error!

However, in JavaScript, the situation is very different, the last element must not have a comma at the end, otherwise it is a grammatical error.

var a = new Array (1,2,3); Correct
var a = new Array (1,2,3,);//Error

For an object, there is also no trailing comma.

var o = {name: ' Zhao ', age:12}; Correct
var o = {name: ' Zhao ', Age:12,};//Error

Although some browsers do it with the greatest tolerance after detecting this error, this is not a uniform behavior. IE series browsers do not tolerate such mistakes.

3 JSON also can't tolerate the comma at the end

{"Name": "Zhao", "Age": 12}//correct JSON format
{"name": "Zhao", "Age": 12,}//Bad JSON format

It should be noted that JSON is a common data format, regardless of the specific programming language. Various languages use varying degrees of tolerance when decoding JSON. PHP's Json_decode () cannot tolerate the comma at the end.

Json_decode ({"Name": "Zhao", "Age": 12,}); Parsing can cause errors

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