![](/img/trans.png)
[英]JavaScript code or framework for converting columns to rows and rows to columns in HTML table or div grids
[英]Javascript - Converting columns into rows
JS相对较新,因此试图理解此代码,该代码需要一个数组数组并将其列转换为数组。
grid=
[[".",".",".","1","4",".",".","2","."],
[".",".","6",".",".",".",".",".","."],
[".",".",".",".",".",".",".",".","."],
[".",".","1",".",".",".",".",".","."],
[".","6","7",".",".",".",".",".","9"],
[".",".",".",".",".",".","8","1","."],
[".","3",".",".",".",".",".",".","6"],
[".",".",".",".",".","7",".",".","."],
[".",".",".","5",".",".",".","7","."]]
//Turn columns into rows
var transpose = grid =>
grid[0].map(
(_,c) => grid.map(
row => row[c]
)
)
使用常规函数看起来如何?
var transpose = grid => // defining `transpose` as function with parameter `grid`, returning the following expression
grid[0].map( // return values from first row mapped via following function
(_,c) => grid.map( // using second parameter which is an index to do column mapping
row => row[c] // returning the value with index of row but from column
)
)
因此,如果没有此ES6 map
功能,则会嵌套2个循环:
var grid = [[".",".",".","1","4",".",".","2","."], [".",".","6",".",".",".",".",".","."], [".",".",".",".",".",".",".",".","."], [".",".","1",".",".",".",".",".","."], [".","6","7",".",".",".",".",".","9"], [".",".",".",".",".",".","8","1","."], [".","3",".",".",".",".",".",".","6"], [".",".",".",".",".","7",".",".","."], [".",".",".","5",".",".",".","7","."]]; function transpose(grid) { var ret = []; for (var i = 0; i < grid[0].length; i++) { ret[i] = []; for (var j = 0; j < grid.length; j++) { ret[i][j] = grid[j][i]; } } return ret; } // use map for pretty printing the matrix console.log(grid.map(row => row.join(' '))); console.log(transpose(grid).map(row => row.join(' ')));
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