strings, builtin: remove strings.Builder.clear(), fix array.clear() not working in the JS backend (#23992)

vlib/builtin/js/array.js.v

@@ -317,7 +317,7 @@ pub fn (mut a array) reverse_in_place() {
 
 pub fn (mut a array) clear() {
 	#a.val.arr.make_copy()
-	#a.val.arr.arr.clear()
+	#a.val.arr.arr.length = 0
 }
 
 // reduce executes a given reducer function on each element of the array,

vlib/strings/builder.c.v

@@ -59,11 +59,6 @@ pub fn (mut b Builder) write_runes(runes []rune) {
 	}
 }
 
-// clear clears the buffer contents
-pub fn (mut b Builder) clear() {
-	b = []u8{cap: b.cap}
-}
-
 // write_u8 appends a single `data` byte to the accumulated buffer
 @[inline]
 pub fn (mut b Builder) write_u8(data u8) {
@@ -246,7 +241,7 @@ pub fn (mut b Builder) str() string {
 	b << u8(0)
 	bcopy := unsafe { &u8(memdup_noscan(b.data, b.len)) }
 	s := unsafe { bcopy.vstring_with_len(b.len - 1) }
-	b.trim(0)
+	b.clear()
 	return s
 }
 

vlib/strings/builder.js.v

@@ -22,10 +22,6 @@ pub fn (mut b Builder) write_byte(data u8) {
 	b << data
 }
 
-pub fn (mut b Builder) clear() {
-	b = []u8{cap: b.cap}
-}
-
 pub fn (mut b Builder) write_u8(data u8) {
 	b << data
 }
@@ -67,7 +63,7 @@ pub fn (mut b Builder) str() string {
 
 	#for (const c of b.val.arr.arr)
 	#s.str += String.fromCharCode(+c)
-	b.trim(0)
+	b.clear()
 	return s
 }