5/20/2023 0 Comments What is es6Hence, the introduction of let in the wrong position. (It could also be used to assign a constant value.) The problem arises because the var keyword was introduced before const was supported, so backwards compatibility dictates that var doesn't necessary mean a variable. Logically, you could let a constant equal something as well, since the job of the "let" keyword is to assign memory. Let adds this semantic inconsistency to Javascript. def is a shorthand for "define function" - completely missing the point of what is being "def". Some other languages use a prefix to the actual object instead of the object when declaring it (e.g. It exists in contrast to const which of course means "constant" - which is the opposite of variable. It's a declaration, in other words, an initialization and assignment. Var confuses us by referring to the same variable throughout the function. Start over, but change `let` to `var`. Let y = 2 // `let` declares a variable in this block Their example is a realistic one that sets onclick handlers in a web page. Mozilla Developer Network gives an example where var does not work as intended. = produces some "surprising" results, so just adopt =.) (In another performance of "The Better Parts", Doug says why = was added rather than fixing the problems of =. Realistically, your impression is right on for ES6: Adopt let and const. But to be clear, you can still modify the object y.hi = 'SO' unless you freeze it.) That's often preferrable since it keeps something from accidentally changing out from under you. After let x = you can reassign to x, while after const y = x you cannot reassign to y. Var might possibly still be useful in an extreme case like machine-generated code, but I'm stretching hard there. A var has function scope (it declares a variable that's visible throughout the function) even though it looks like it has block scope. for programmers with expectations set by languages with block-scope. The point is, let avoids a source of misunderstanding, esp. Doug Crockford discusses let at this point in his talk, " The Better Parts".
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