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Chapter 5. Building JavaScript Expressions > Understanding Operator Precedence

Understanding Operator Precedence

You'll often use simple expressions that contain just two values and a single operator. In practice, however, many expressions you use will have a number of values and operators. In these more complex expressions, the order in which the calculations are performed becomes crucial. For example, consider the expression 3+5*2. If you calculate from left to right, the answer you get is 16 (3+5 equals 8 and 8*2 equals 16). However, if you perform the multiplication first and then the addition, the result is 13 (5*2 equals 10 and 3+10 equals 13). In other words, a single expression can produce multiple answers depending on the order in which you perform the calculations.

To control this problem, JavaScript evaluates an expression according to a predefined order of precedence. This order of precedence lets JavaScript calculate an expression unambiguously by determining which part of the expression it calculates first, which part second, and so on.


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