Comparison between regular arrays and associated arrays in Javascript

First, let's take a look at the array classification: from the array subscript into an index array, associated array/* index array, that is, the commonly referred array */varary1 [,]; // retrieve array elements by index, starting from 0 (of course some languages start from 1). The index is actually in order... syntaxHighlighter. all ();

First, let's look at the array classification:

Index Array and associated array by array subscript
/* Index array, which is usually an array */
Var ary1 = [1, 3, 5, 8];
// Retrieve array elements by index, starting from 0 (of course some languages start from 1). The index is actually a ordinal number, an integer number.
Ary1 [0];
Ary1 [1];
Ary1 [2];
Ary1 [3];
 
/* Associated array, which is an array that is accessed by subscripts of the non-ordinal number type. In python, it is called a dictionary */
Var ary2 = {}; // The value is a non-ordinal number (number). Here it is a string.
Ary2 ["one"] = 1;
Ary2 ["two"] = 2;
Ary2 ["thr"] = 3;
Ary2 ["fou"] = 4;

 

Question: You can test it as follows:

Alert (arry1.length); // return value: 4

 

Alert (arry2.length); // return value: 0

 

What is this? Because js is a weak type language, all js types are objects,

For example, var arr = [];
Arr [0] = 1;
Arr [1] = 2;
Arr [2] = 3;
Arr ["s"] = 4;
At this time, you call arr. s, which is equivalent to calling the s attribute of the arr object, but this is arr. length, which is still 3.

Summary: although the correlated array can be used as a subscript by a string, this subscript does not support parameter value passing. In other words, it sounds intelligent to take whatever you need, in fact, you still need to manually write down the value.

 

 

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