refactor: make code clean by removing unused/unnecessary codes

[cimfalab]

• refactor(component): remove unused variable and return value
  • Array#splice() changes itself and returns deleted elements. So assigning return value is not necessary in this case.
• refactor(visible): remove unexecuted codes by above condition
• refactor(scrollEnd): remove unnecessary radix parameter for parseFloat()
  • parseFloat() has only one argument unlike parseInt
• refactor(pauseResume): remove unnecessary condition check
  • type is set to constant "fx" above
• test(agent): remove uninitialized variable use and fix parseFloat()
• test(class): use previously calculated variable 'nChangedMultiB'
• test(component): remove redundant 'var' because it is function scoped
• test(flicking): move 'var' declaration under its function
• test(infiniteGrid): remove unused variable 'self'
• test(persist): add initialization check for test set-up
• test(rotate): remove redundant 'var'
• test(visible): remove unused variables

And I think 'agent' variable in test(rotate) is not necessary, so I added a note for it.

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