Commit df3260a

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Original file line number	Diff line number	Diff line change
`@@ -14,6 +14,7 @@ true + false = 1`
`14`	`14`	`" -9 " - 5 = -14 // (4)`
`15`	`15`	`null + 1 = 1 // (5)`
`16`	`16`	`undefined + 1 = NaN // (6)`
	`17`	`+" \t \n" - 2 = -2 // (7)`
`17`	`18`	```
`18`	`19`
`19`	`20`	1. The addition with a string `"" + 1` converts `1` to a string: `"" + 1 = "1"`, and then we have `"1" + 0`, the same rule is applied.
`@@ -22,3 +23,4 @@ undefined + 1 = NaN // (6)`
`22`	`23`	4. The subtraction always converts to numbers, so it makes `" -9 "` a number `-9` (ignoring spaces around it).
`23`	`24`	5. `null` becomes `0` after the numeric conversion.
`24`	`25`	6. `undefined` becomes `NaN` after the numeric conversion.
	`26`	+7. Space characters, such as `\t` and `\n`, are trimmed off string start and end when a string is converted to a number. So a string `\t \n`, similarly to an empty string, becomes `0`.

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Original file line number	Diff line number	Diff line change
`@@ -21,6 +21,7 @@ true + false`
`21`	`21`	`" -9 " - 5`
`22`	`22`	`null + 1`
`23`	`23`	`undefined + 1`
	`24`	`+" \t \n" - 2`
`24`	`25`	```
`25`	`26`
`26`	`27`	`Think well, write down and then compare with the answer.`

Lines changed: 3 additions & 1 deletion

Original file line number	Diff line number	Diff line change
`@@ -119,7 +119,7 @@ The method [arr.slice](mdn:js/Array/slice) is much simpler than similar-looking`
`119`	`119`	`The syntax is:`
`120`	`120`
`121`	`121`	```js
`122`		`-arr.slice(start, end)`
	`122`	`+arr.slice([start], [end])`
`123`	`123`	```
`124`	`124`
`125`	`125`	It returns a new array copying to it all items from index `start` to `end` (not including `end`). Both `start` and `end` can be negative, in that case position from array end is assumed.
`@@ -136,6 +136,8 @@ alert( arr.slice(1, 3) ); // e,s (copy from 1 to 3)`
`136`	`136`	`alert( arr.slice(-2) ); // s,t (copy from -2 till the end)`
`137`	`137`	```
`138`	`138`
	`139`	+We can also call it without arguments: `arr.slice()` creates a copy of `arr`. That's often used to obtain a copy for further transformations that should not affect the original array.
	`140`	`+`
`139`	`141`	`### concat`
`140`	`142`
`141`	`143`	`The method [arr.concat](mdn:js/Array/concat) creates a new array that includes values from other arrays and additional items.`

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