Question about JS control of different frames

JS controls different frames. if you have any questions, ask the webpage that there are two frames, one for main and the other for left. now there is an input box in main, when I enter the code and press enter, the corresponding content will be displayed in leftframe. The problem is that I want to capture a key, such as the keys, in the main input box, my question about controlling different frames with the cursor from JS
You guys have a question
There are two frames on the webpage, one being main and the other being left. now there is an input box in main. when I enter the code and press enter, the corresponding content will be displayed in the left Frame, my problem now is that when I want to capture a key in the main input box, for example, the cursor key, I automatically jump to the left frame input box and enter the amount.
I am not familiar with how to operate this cursor in js and focus it on the input box of left frame.
Thanks

------ Solution --------------------
Replace leftFrame, yourText.
Prarent. leftFrame. yourText. fouce ();