slice-with-context
Basically String.prototype.slice
, but with a configurably-positioned window
around it, showing context.
npm i slice-with-context
The module exports 1 function:
sliceWithContext(inputString, windowSize, cutOffset, cutLength [, windowLeftBias] [, overflowLeftBias])
Params:
-
inputString
:String
string to cut -
windowSize
:Number
size of window -
cutOffset
:Number
cut start position, in characters -
cutLength
:Number
cut length, in characters -
windowLeftBias
:Number
between 0–1 [optional] if there is space left in the window on both sides of the sliced part, this option determines what proportion of what's left to show on the left rather than the right.0 means only show context on the left. 1 means only show context on the right. (default 0.5)
-
overflowLeftBias
:Number
between 0–1 [optional] if the window is too small to show the sliced part fully, this option determines which part of the sliced part should be shown.0 means only show the very start of the slice. 1 means only show the very end of the slice. Intermediate values mean to show that far along the middle of the slice. (default 0)
Throws if the slice parameters would miss the string entirely, by being too long, offset past it, or other such obviously wrong nonsense.
Clamps windowLeftBias
and overflowLeftBias
to 0–1.
Example
Suppose you want to slice the bold part out of 123456789, showing a total of 6 characters; the sliced part and the rest just for context because you have space to spare.
const sliceWithContext = require('slice-with-context')
const output = sliceWithContext(
'1234567890',
6, // windowSize
4, // offset
4, // length
0.5, // windowLeftBias
0, // overflowLeftBias
)
console.log(output)
{ fit: true, withContext: '456789', visibleSlice: '5678', fullSlice: '5678', position: { offset: 1, length: 4 } }
If you're writing a compiler or something, you might render that as—
456789
^^^^
Or use ANSI colour codes, or some such.
Specific situations
Equal amounts of context on either side
const sliceWithContext = require('slice-with-context')
const output = sliceWithContext(
'1234567890',
6, // windowSize
4, // offset
4, // length
0.5, // windowLeftBias
0, // overflowLeftBias
)
console.log(output)
{ fit: true, withContext: '456789', visibleSlice: '5678', fullSlice: '5678', position: { offset: 1, length: 4 } }
With context only on the left
const sliceWithContext = require('slice-with-context')
const output = sliceWithContext(
'1234567890',
6, // windowSize
4, // offset
4, // length
1, // windowLeftBias
0, // overflowLeftBias
)
console.log(output)
{ fit: true, withContext: '345678', visibleSlice: '5678', fullSlice: '5678', position: { offset: 2, length: 4 } }
With context only on the right
const sliceWithContext = require('slice-with-context')
const output = sliceWithContext(
'1234567890',
6, // windowSize
4, // offset
4, // length
0, // windowLeftBias
0, // overflowLeftBias
)
console.log(output)
{ fit: true, withContext: '567890', visibleSlice: '5678', fullSlice: '5678', position: { offset: 0, length: 4 } }
Left context only, but with no space
const sliceWithContext = require('slice-with-context')
const output = sliceWithContext(
'1234567890',
6, // windowSize
0, // offset
4, // length
1, // windowLeftBias
0, // overflowLeftBias
)
console.log(output)
{ fit: true, withContext: '123456', visibleSlice: '1234', fullSlice: '1234', position: { offset: 0, length: 4 } }
Both-sided context, but no space at end
const sliceWithContext = require('slice-with-context')
const output = sliceWithContext(
'1234567890',
6, // windowSize
6, // offset
4, // length
0.5, // windowLeftBias
0, // overflowLeftBias
)
console.log(output)
{ fit: true, withContext: '567890', visibleSlice: '7890', fullSlice: '7890', position: { offset: 2, length: 4 } }
Insufficient space in window, truncated to show start
const sliceWithContext = require('slice-with-context')
const output = sliceWithContext(
'1234567890',
6, // windowSize
0, // offset
8, // length
1, // windowLeftBias
1, // overflowLeftBias
)
console.log(output)
{ fit: false, withContext: '123456', visibleSlice: '123456', fullSlice: '12345678', position: { offset: 0, length: 6 } }
Insufficient space in window, truncated to show end
const sliceWithContext = require('slice-with-context')
const output = sliceWithContext(
'1234567890',
6, // windowSize
0, // offset
8, // length
1, // windowLeftBias
0, // overflowLeftBias
)
console.log(output)
{ fit: false, withContext: '345678', visibleSlice: '345678', fullSlice: '12345678', position: { offset: 0, length: 6 } }
Tests
That's the code examples above! They're run with txm.