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This article mainly explains "javascript array subscript where to start," interested friends may wish to take a look. The method introduced in this paper is simple, fast and practical. Let's take you to learn "javascript array subscript where to start"!

Javascript array subscripts start at 0. Reasons: 1. Starting from 0, you can reduce a subtraction operation, reduce CPU instruction operations, and improve CPU efficiency;2. The address of physical memory starts from 0.

Operating environment of this tutorial: Windows 7 system, Javascript version 1.8.5, Dell G3 computer.

Javascript array subscripts start at 0.

So why do javascript array subscripts start at 0 instead of 1?

Reason 1: Historical reasons

Languages appear in order from early to late C, Java, JavaScript.

C array subscripts start at 0->Java also->JavaScript also.

Reduce additional learning and understanding costs.

Reason 2: Reduce CPU instruction operations

(1) Subscripts start from 0:

Array addressing--arr[i] = base_address + i * type_size (1)

Where base_address is the first address of array arr, arr0 is the array with offset 0, that is, the first address of array arr;i is the offset, type_size is the number of bytes of array type, for example, int is 32 bits, that is, 4 bytes.

(2) Subscripts start with 1:

Array addressing--arr[i] = base_address +(i -1)* type_size (2)

Comparing the two calculation formulas, we can find that formula (2) requires one more i-1 operation per CPU address, that is, one more subtraction instruction operation.

Arrays, the basic data structure, are frequently used indirectly (as a container base data structure, such as Java's ArrayList) or directly in any high-level programming language, so they consume as little CPU resources as possible. Starting from 0, one subtraction operation can be reduced, improving CPU efficiency.

Reason 3: Physical memory addresses start at 0.

Computer main memory is an array of consecutive byte units, each byte corresponding to a unique physical address, the first byte address is 0.

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