Please help to convert for loop into while loop : Please to convert the for loop below into a while loop

    for (j = 0; s1[j] != '\0'; j++, i++)
			    sen[i] = s1[j];

i tried to convert but got any empty result,not sure what is wrong with this...
 
    while (j= 0, s1[j] != '\0') {
			      j++, i++;
			      sen[i] = s1[j];
		      }

the original code is below :

    #include <stdio.h>
    #include <stdafx.h>

    int main()
    {
	    char s[] = "Bad";
	    char s1[] = "weather!";
	    char sen[10];
	    int i, j;
	    for (i = 0; i<20; ++i){
		    if (s[i] != '\0')
			    sen[i] = s[i];
		    else {
		      sen[i++] = ' ';
		    for (j = 0; s1[j] != '\0'; j++, i++)
			    sen[i] = s1[j];
			    break;
		    }
		    }
	    sen[i] = '\0';
	    puts(sen);
	    }

Thank you