I found this interesting site http://www.howjsay.com. I realized their site name "howjsay" might just be "how to say". Am I right?
Do people say "how to say" as "how j say"?
In some dialects of American English,
How do you say
is pronounced in a way that sounds something like this.
You get there as follows:
The vowels in the non-accented syllables "do" and "you" becomes a schwa, "duh yuh"
The vowel in "do" then drops out completely: "d'yuh"
The "d" and "y" sounds combine into "j": "juh"
Slurring is one of the features of English that makes it different from, say, Spanish (they shorten vowels sometimes but they do not change pronunciation, for example vamos a hablar -> vamos ablar) or Chinese (each syllable is extremely distinct). English has a lot of slurring. The pronunciation of a word changes depending on whether the person is saying something quickly or slowly, in a high register or in a low register, or with a strong accent or a more neutral accent. Pronunciation and spelling are probably the hardest parts of learning English.
As an American English speaker, if I were saying "how to say" fast, I would say it something like...
how duh say
In IPA, the word "to" transforms from /tu/ to /ɾə/
As a language learner, I would advise you to not worry about these changes in pronunciation and to just focus on learning the normal pronunciations of everything. Pronunciation changes are often different in different countries and areas, so I imagine trying to learn all the pronunciation changes for a certain area without living in that area for a long time will just end up confusing and frustrating you.
In answer to your original question, "howjsay" could definitely be a clever way to write "how to say". "j" makes a "y" sound in IPA, so "howjsay" could sound something like...
how yuh say
I've heard this before. It is a slur of "how (do) you say?"