The projection of the vector i+j+k on the vector j is :

$\vec{v_1} = \hat{i}+\hat{j}+\hat{k}$

$\vec{v_2} = \hat{j}$

so projection of $\vec{v_1}$ on $\vec{v_2}$ is $\vec{v_1} . \vec{v_2}$

= 1