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JavaScript JavaScript Loops, Arrays and Objects Simplify Repetitive Tasks with Loops Exiting Loops

Ian Hock
Ian Hock
7,604 Points

I was wondering why we create an empty variable called guess; ? I've erased it and the program still functions?!

Originally I thought guess; stored the value of whatever they enter in the prompt. But the way that block evaluates guess in the (while, do/while, ) loop structure it seems like it shouldn't need it.

3 Answers

Steven Parker
Steven Parker
229,967 Points

Assigning a variable that has not been declared causes it to be created as a global. While this is perfectly legal in terms of the language itself, it is considered a "best practice" to define all variables before they are used. This can be helpful in determining the intended scope of the variable.

JavaScript also has a "strict" mode, and when it is used it makes it illegal to use a variable that has not been declared. So developing the habit of always declaring your variables will simplify development if you ever work in strict mode.

your program might work differently on larger projects as it declares a global variable and global variable may change if you use another variable with same name;