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sort.service.ts
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sort.service.ts
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import { Injectable } from '@angular/core'
@Injectable({
providedIn: 'root'
})
export class SortService {
// usage:
// array = this.sortservice.mergeSortObj(array, 'row_from', 'desc'|'asc')
constructor() { }
private static CMP_GREATER_THAN = 1
private static CMP_LESS_THAN = -1
private static CMP_EQUAL = 0
private compare(a, b):number {
if(a < b){
return SortService.CMP_LESS_THAN
}
else if(a > b) {
return SortService.CMP_GREATER_THAN
}
else if(a === b) {
return SortService.CMP_EQUAL
}
// not comparable -> error
console.error("Cant compare", a, " and ", b)
return SortService.CMP_EQUAL
}
public mergeSortObj(arr=[], attr=null, dir:'desc'|'asc'='desc', compareFunction?:(a,b)=>number) {
if (arr.length === 0) {
return []
}
if (attr === null || dir === null) {
return null
}
let cmp = typeof compareFunction != "undefined" ? compareFunction : this.compare
var left = []
var right = []
var pivot = arr[0]
for (var i = 1; i < arr.length; i++) {
if (cmp(arr[i][attr], pivot[attr]) === SortService.CMP_GREATER_THAN) {
if(dir=='asc')
right.push(arr[i])
else
left.push(arr[i])
} else {
if(dir=='asc')
left.push(arr[i])
else
right.push(arr[i])
}
}
return this.mergeSortObj(left, attr, dir).concat(pivot, this.mergeSortObj(right, attr, dir))
}
}